The Sanskrit word bhakti means devotion, a profound interest in God. As mentioned in the Śāṇḍilya Bhakti Sūtras (1.2) bhakti consists in para—anurakti, which translates to "a great attachment to God and all that is related to the Divine".
Bhakti—yoga is the path of the heart, of divine love, devotion. It deals with the emotional aspect of man. As Swami Vivekānanda expressed it, "it is a search for God that starts, continues, and ends with love".
Within Hinduism, the term bhakti is used to denote devotion to a certain aspect of Divinity, a specific deity. Hence, the followers of Śaivism see bhakti in relation to Lord Śiva while the followers of Vaiṣṇavism see it with Lord Viṣṇu or one of his incarnations.
 Bhakti is devotion, not emotion. In the process of bhakti—yoga, the devotee, or bhakta, consciously projects his feelings toward Divinity. Every emotion has force and energy and the emotional plane is extremely powerful. Uncontrolled, this power can become destructive because emotions can disperse and divide us, as they lead in different directions. Bhakti—yoga unites the emotions in an integrative process. Through worship, prayer, chanting, and ritual, it channels unconscious feelings and focuses them on the Divine. It is a transformation of feelings from emotion to devotion.
This path is especially recommended for those of emotional character. Bhakti—yoga is, no doubt, the easiest path of spiritual growth and development for any person, regardless of race, nationality, social condition, or intellectual level. The only requisites are a sincere faith in God, contemplation of all that is related to the Divine, and a great desire to love intensively.
After all, in every being there is a need to love. Some place this love in a country, others in family, some in possessions and money, and some in their dog. Nonetheless, these are but partial or limited manifestations of love. Nothing and no one can satisfactorily reciprocate our love but God. Only by directing our love toward the root, the origin, the source, God, only then shall we shower everything and everyone with love.
This is illustrated in this beautiful verse from the Bhāgavata Purāṇa (4.31.14):
yathā taror mūla—niṣecanena
tṛpyanti tat—skandha—bhujopaśākhāḥ
prāṇopahārāc ca yathendriyāṇāṁ
tathaiva sarvārhaṇam acyutejyā
"When the root of a tree is watered, each and every one of its parts, the trunk, the branches, and the leaves is filled with energy. Similarly, when the stomach receives food, all of the bodily limbs and the senses become powerful. The worship directed to the Divinity satisfies all of the devas."
Love is destined, ultimately, for God, in the same way that food is destined for the mouth. Even though the body has other orifices, only food placed in our mouth will satisfy the body. Only love to God, or bhakti, can reach and satisfy all. In fact, it is the only love that can satisfy our lives.
The bhakta is not searching for "spiritual gains", but to make himself open and accessible enough so as to be taken by Divinity.... Bhakti is the wisdom that teaches us how to use our hearts as a path and doorway toward our ideal.... The path of devotion is simple in the sense that it does not require concentration techniques or effort in meditation. A lover does not require encouragement to think of his beloved. Even if he desires to stop, he cannot cease from thinking of his beloved.  In bhakti, the mind flows naturally and disappears into the beloved.... Love is an acid powerful enough to dissolve the ego, which is the opposite of love. Darkness cannot withstand the light, just as the ego cannot sustain itself in the presence of love. There is no better antidote for the ego than love and pure devotion. When we love others, we focus on the other person. Their happiness makes us throb. Their grief saddens us. By loving, we prove that we are not what is important and our personal interests cease to be significant. To love is to sacrifice. To love is to stop negotiations — to give everything without expecting anything in return. To love is to be less.... To love is to disappear.
Real religion does not consist only in vestments and symbols such as hats, beards, crucifixes, saffron clothes, and cathedrals but in love of and devotion to the Divine.
Bhakti—yoga transforms man, leading him from the instinctive to the divine plane. He miraculously detaches his senses from mundane and corporal enjoyment and concentrates his attention on God, reaching intoxication with prema—bhakti, or the pure and crystalline love for God.
Yoga and love are actually synonymous because both are a union.... Bhakti is the yoga of art. The paintings we see in churches and temples, the religious statues, the hymns, songs, and bhajanas of different religions are all manifestations of the spirit of bhakti. These works are an expression of the soul's thirst for glorifying the Supreme, or kīrtana. This is what the Bhagavad—gītā (9.14) describes as the real occupation of great souls:
satataṁ kīrtayanto māṁ
yatantaś ca dṛḍha—vratāḥ
namasyantaś ca māṁ bhaktyā
nitya—yuktā upāsate
"Always glorifying me, striving with great determination and prostrating before Me, these great souls adore Me perpetually with devotion."
The Danger of Bhakti—yoga
As everything in life, every spiritual path has its benefits but also its dangers if it is not utilized properly. The danger of bhakti, which is the same as with all religions, is fanaticism.
When great and elevated ideals are distorted by egoistic and sectarian people, instead of serving as means for growth and development they lead the masses not only to obscurantism but to spiritual and cultural stagnation. I am especially referring to the religious sectarianism that represents an attitude completely antagonistic to the universal spirit of bhakti with its pluralist vision of the great sages of Hinduism.
It is a disgrace that even now, confrontations, enmities, and hate between human beings for religious motives continue. It is shameful that people cannot publicly declare their beliefs because they fear the reprisal of fanatic and extremist religious groups, and that ancient respectable Eastern religions such as Hinduism are not only undervalued in the West but are dismissed as "sects" or "cults". This attitude is a product of Western culture's unfortunate and unjustified superiority— complex in which outdated colonialist attitudes still prevail.
God is one and the same for all humans. In the same way that people in the United Kingdom use the English word "water" while the people in Chile use the Spanish word "agua", God is called by different names, depending on the religion. It is ridiculous to think that the language determines the substance. Humanity must understand the simple reality that God is one, and even though Divinity might be called by different names in various religions and cultures, these names all have the same meaning.  
 There are no such things as "our" God and "your" God. God is one, in reality only God is....
The follower in the path of bhakti—yoga must be vigilant against this dangerous distortion and the spiritual illness that results in sectarianism and fanaticism.
Bhakti—yoga and the Mundane Desires
In the path of bhakti, it is essential to try and reduce crude sensual satisfaction because desires and lust are obstacles for the development of devotion. The devotee's heart is nourished by but one desire — God — and our devotion and attraction to the Divine will diminish in proportion to the mundane desires we indiscriminately satisfy. Likewise, by trying to reduce our sensual satisfaction we will notice a proportional augmentation in our devotion to Divinity and spiritual life.
 In real love, there is no place for any other desire that is not for the beloved. In the same way that when people marry they sanctify each other in body and soul, and as a couple, they demand mutual exclusivity, in bhakti, which is a divine romance, we exclusively consecrate ourselves to God, our beloved, in body and soul, and renounce desires to satisfy our corporal senses. The bhakta not only intellectually comprehends that he is not the physical body, but also tries to live according to this truth.... the true bhakta does not even aspire to enlightenment or liberation.
The Nine Steps of Bhakti—Yoga
According to the Bhāgavata Purāṇa (7.5.23—24), the process of bhakti—yoga is made of nine different steps:

"Prahlāda Mahārāja said, ‘There are nine processes that are considered pure devotional service: hearing and glorifying the Holy Name, the form, the qualities, the paraphernalia and transcendental pastimes of Lord Viṣṇu, remembering them, serving the lotus feet of the Lord, offering respectful adoration with sixteen types of items, offering prayers, being His servant, considering Him the best of friends, and surrendering everything to Him (in other words, serving with body, mind, and speech). He, who by these nine methods, dedicates his life to the service of Kṛṣṇa, is considered the wisest person, for he is established in wisdom.'"
These nine processes are also mentioned in the Viṣṇu Purāṇa.

1. Śravaṇa means to listen. Listening to the words of saints and sages who constantly dedicate themselves to glorifying the Lord and who take delight in talking and conversing about the transcendental pastimes of the Supreme Lord. The mind is absorbed in the sacred stories. An appreciation and attachment is developed in our hearts and our subconscious by constantly hearing His Glories.
In this first step of bhakti we open, and make ourselves accessible to receive the seed of devotion in the fertile ground of our heart from a spiritual master. Bhakti cannot be intellectually understood; it is not a question of methods or techniques. Bhakti, or pure love for God, is something like a virus that infects. The great souls and pure devotees of the Lord are those souls who become elements infected by Divine love. This is the principle reason for all of the lectures and sādhu—saṅga, association with great souls. Hence the great importance of satsaṅga, association with a sage who has realized the Truth, who has seen the real....

2. Kīrtana means glorifying and praising Divinity. Kīrtana is chanting the glories and the Holy Names of the Lord. The devotee recites the Holy Names of God according to the aspect or Iṣṭa—devatā to which his heart is inclined. If the devotee is a follower of Lord Kṛṣṇa, it is highly recommended to perform the recitation of the mahā—mantra, Hare Kṛṣṇa Hare Kṛṣṇa Kṛṣṇa Kṛṣṇa Hare Hare Hare Rāma Hare Rāma Rāma Rāma Hare Hare, with a rosary of tulasī beads called mālā. For a devotee of Lord Śiva, it is better to repeat with a rosary of rudrākṣa the mantra Oṁ namaḥ Śivāya. The recitation of God's Holy Names is extremely recommended in the Vedic scriptures.
In the Bhāgavata Purāṇa (2.1.11), the spiritual text of the bhaktas, Śukadeva Gosvāmī tells Mahārāja Parīkṣit the following:
etan nirvidyamānānām
  icchatām akuto—bhayam
yogināṁ nṛpa nirṇītaṁ
  harer nāmānukīrtanam
"O King! The constant chanting of the Holy Names of God, following the path of the great spiritual authorities, is the way, without doubt or fears, where all can succeed, those who are free of all mundane desires, as much as those who are desirous of material enjoyment, and also those who are self satisfied in the virtue of transcendental wisdom."
The recitation of God's Names, or mantras, is called japa and is a very important meditation; it can be a verbal, semi—verbal, or mental repetition. It is fundamental that the mantra is received in a Vedic initiation ceremony, dīkṣā, directly from one's own spiritual master, who should be a bona fide spiritual master within a line of disciplic succession or paramparā. When the Names of God are chanted loudly it is called saṅkīrtana. Within any religion we can find hymns and devotional songs that fall into this category of kīrtana. For example, Lord Caitanya organized an extraordinary movement of saṅkīrtana by chanting the mahā—mantra in Bengal, five hundred years ago.

3. Smaraṇa: means remembrance or remembering God.  In the Viṣṇu Purāṇa we find a beautiful verse that says, "Simply by remembering Divinity, any living being is eligible for all that is auspicious. Therefore, let me always remember the Lord, who is unborn and eternal".
Remembering comes right after the previous two steps, because if we hear about the glories and pastimes of the Lord and chant His Names, remembering Him will be natural and spontaneous. The remembrance of God, our Iṣṭa—devatā, and His related sacred stories, should be constant, even in our dreams. From the first moment we open our eyes in the morning, our first thought, first idea, should be related to God, the form of the Iṣṭa—devatā, His Name, His holy devotees, our spiritual master, and so on.
Do not think that the constant remembrance of Divinity is a simple or easy sādhanā. Just try and see how difficult it is to focus the mind in the Divine. There is no evil in the world except the forgetting of our true origin.... Divinity....
Forgetfulness of the true and authentic essence is the cause of pain and misery....
Remembrance of God is forgetfulness of the world....
Reminiscence of God is forgetfulness of māyā, illusion....
Remembrance of the One God is forgetfulness of the world of names and forms, the world of differences....
A constant remembrance of God is remembering what we really are and forgetting what we imagine ourselves to be....
Remembering God is remembering what we never knew... and what we can ask no one but our heart....

4. Pāda—sevana is the service to the lotus feet of Divinity. Pāda in Sanskrit means foot  and sevana means service. In the Vedic art this concept is personified by Lakṣmī, who massages the feet of Lord Viṣṇu. Only by seeing all of Humanity, without differentiations of class, race, religion, or gender, as the sacred lotus feet of the Lord, we can serve the Lord by making efforts for the well being of others and sacrificing ourselves for the happiness of others. After all, as it is written in the Bhagavad—gītā (15.7), the human being is a manifestation of the Divine:
"An eternal part of Me became a living soul in the world of life; it attracted the five senses and the mind, which is the sixth — all reside in nature."  
 Therefore, serving the human being is serving God....
Live with the constant question: "What can I do now as to contribute, even a little, to the happiness of my fellow men?" Pāda—sevana is devotional service, and this is also the meaning of the term bhakti—yoga in many Vedic scriptures, such as the Bhakti—rasāmṛta—sindhu, where Śrīla Rūpa Gosvāmī (1.1.2) explains it:
"Bhakti, or devotional service, means engaging our senses in the service of the Lord, the true master of all senses. When the soul renders service to God, two effects come through: first, one is liberated from any kind of illusory identifications and second, his senses are instantly purified, all for the simple act of engaging in the service of God."
This verse is also mentioned in the Śrī Caitanya—caritāmṛta (Madhya 19.170).
We understand from this important verse that devotional service allows us to experience that the senses, which, because we think them to be ours, we constantly try to satisfy them; in fact, the senses belong to God, "the Lord of the senses", who is their only true and authentic master. Therefore, it is appropriate to place and utilize them in His service. Through devotional service, a situation is created where we become aware that our life, and all that we believe to be ours, is really the possession of God, and our service becomes a process of surrender to the Divine.

5. Arcana means to worship the Divine, and more precisely the worship of God and the deity in the temple.  For example, a beautiful Vedic ceremony takes place daily in our temples and centers. It is called maṅgala—ārati and consists of chants for the glorification of the Supreme Lord.
The devotee who performs the offering is called pūjārī and he offers a series of auspicious objects such as flowers and incense, while others sing ancient Vedic mantras accompanied by cymbals, harmoniums and mṛdaṅgas. The worship is performed before a deity or an image of the chosen aspect of Divinity.
Learning to perform Vedic arcana correctly in a temple, to be an expert pūjārī, can take many years of intense studies. The ceremonies have to be carried out according to strict rules, with specific mantras for each part of the worship process. However, deity worship at home can be less demanding and very pleasant.
It is beneficial to dedicate a room in your house for worship because besides using it for worship, meditation, and prayer, you will be able to create radiating positivity, and by hanging up portraits of different Hindu saints and sages thus create an inspiring and meditative environment for others.
It is important to worship and offer the Lord flowers, incense and water, but it is essential to remember that everything has to be offered with devotion. Without love and devotion the worship can easily become a ritual and social tradition without spiritual value.
Lord Kṛṣṇa says in the Bhagavad—gītā (9.26):
"If a person offers Me, with love and devotion, a leaf, a flower, a fruit, or water, I will accept it."
 This clearly establishes that the Supreme Lord does not need leaves, flowers, fruits, or water, and that the real condition for the acceptance of this worship is the spirit of the devotee. The offering should reflect a sweet phenomenon that happens in the heart of the worshipper. It is important to note that deity worship manifests naturally out of the devotee's devotion; it is not a necessity of the Divine. As it is the kind of meditation in which we concentrate upon Divinity in a world of names and forms, in this way we remember that God is not only found within us but also outside. The idea of inside and outside is actually a limitation, based on the false concept of the ego, which we take as a point of reference and then create imaginary directions. Whatever is found on one side of the ego idea, we call "inside" and in the other direction, "outside".
 
6. Vandana consists of prayers, reverences, and prostrations before God. A great example of vandana can be found in one of the two greatest classic epics of Hinduism, the Rāmāyaṇa, when King Bharata worshipped the sandals of Lord Rāma.
Prayer is powerful. For example, in the Nṛsiṁha Purāṇa we find a beautiful verse that says, "Any person who approaches the deity of Lord Kṛṣṇa and prays is immediately saved from all reactions to past sinful activities and, without a doubt, becomes eligible to enter in Vaikuṇṭha—loka".
The prayers and reverences of the devotee before the deity are an expression and exteriorization of the devotion and love he experiences in his heart, which also manifests in his constant approach of prayer and reverence toward every being, toward every living entity, realizing that behind this reality of names and forms, his beloved Lord is found, who is the one that abides behind the diversity. This spirit will reflect in his dealings with others as he will be free from racism and sectarianism.
 
7. Dāsya is a profound feeling of being a loving servant to your master. Living in the spirit of a servant leads to happiness and a life full of meaning. In our society we all try, in one way or another, to be the managers and controllers. With a spirit of a servant, we can go about our daily chores and live in the world with a constant and profound feeling that all that we have and are, all that we see, is owned and controlled by the Supreme Lord. We desire to live with chains of devotion that transform us into slaves of love. It is a slavery of bliss.
It is to change the exploitative attitude of using everything and everyone for our own benefit and convenience. It is to abandon, out of love, our fears of being exploited and utilized in the service of God.
Abandoning our egoistic ambitions of possessiveness, and making ourselves accessible to be taken by God. It is to abandon our inclinations to enjoy and discover the authentic bliss of being enjoyed upon, letting the place of the true enjoyer to God. This spirit is perfectly exemplified in the gopīs of Vṛndāvana, and especially in Śrīmatī Rādhārāṇī, the principal and most beloved gopī of Lord Kṛṣṇa.
 
8. Sakhya is the cultivation and development of a profound feeling of transcendental friendship with the Supreme Lord. The devotee reaches a personal relation of intimacy with the Lord, who is no longer felt to be distant and abstract, but as the best and closest friend. This feeling is not due to the error of humanizing God but of man elevating himself. Remember that friends are not like relatives, meaning, one is not born with them, but rather, they are chosen by the heart.
We find a beautiful example of sakhya—bhakti in the Mahābhārata, when Lord Kṛṣṇa talks to Arjuna in the Bhagavad—gītā (4.3):
 
 "This ancient wisdom of relating to the Supreme is now told by Me to you, for you are my devotee as well as my friend, and therefore capable of understanding the transcendental mystery of this wisdom."
 Within the great classical Hindu epic, the Rāmāyaṇa, we find the example of Sugrīva, the son of Sūrya, the Vedic Sun God, who engages in this kind of relationship with Rāma. It is interesting to find this spirit of intimate friendship with God in other religious traditions.
One of the most impressive for me was the Jewish Hassidic saint Rabbi Nachman of Bresslov. This great master called his meditation in Hebrew hitbodedot or "being in solitude", which consists of finding a secluded place, sitting and opening your heart to the Lord, telling Him your problems, your sadness, your pain, just as one opens and speaks his heart to an intimate friend.
Rabbi Nachman used to say that there is a level of realization in which, no matter how difficult the situation we are in might be, we should not give up because in this state of consciousness, we realize that the powerful Whole is found always with us, constantly by our side.
 
9. Ātma—nivedana means complete surrender to the Divine, God, in body, speech, mind, and soul.
The Śrīmad Bhāgavatam (11.29.34) says:
 "A person who renounces and abandons all fruitful activities and completely offers himself to Me, desirous to serve me, realizes liberation from the cycle of birth and death and shares my own opulence."
 Ātma—nivedana is living every moment with absolute trust in life, existence, and God within our heart. This is a highly elevated state of realization where the devotee surrenders everything he has, including himself in body, mind, and soul to God. It is the realization that one never possessed anything. The bhakta surrenders all concept of "I" and "mine".... He is detached from any idea of possession.... His existence is divined.
Surrender is, in a certain way, to die.... Surrender has the taste of death, as love is an acid powerful enough to dissolve the ego....
The more we love — the deeper we love, the closer we feel to death, the more we lose ourselves.... Getting lost, that is truly finding ourselves.... Love is dissolving yourself into the Whole in order to really be because to truly be is to be in God....