Bhakti-rasāmṛta-sindhu is divided into four parts, just as the ocean is sometimes divided into four parts, and there are different sections within each of these four divisions. Originally in Bhakti-rasāmṛta-sindhu, the ocean is divided like the watery ocean into east, west, north and south, while the sub-sections within these different divisions are called waves. As in the ocean there are always different waves, either on the eastern side, the western side, the northern side or the southern side, so similarly Bhakti-rasāmṛta-sindhu has different waves. In the first part there are four waves, the first being a general description of devotional service. The second concerns the regulative principles for executing devotional service, and the third wave devotional service in ecstasy. In the fourth is the ultimate goal, love of God. These will be explicitly described along with their different symptoms.
The authorized description of bhakti, or devotional service, following in the footsteps of previous ācāryas, can be summarized in the following statement by Śrīla Rūpa Gosvāmī: "First-class devotional service is known by one's tendency to be fully engaged in Kṛṣṇa consciousness, serving the Lord favorably." The purport is that one may also be in Kṛṣṇa consciousness unfavorably, but that cannot be counted as pure devotional service. Pure devotional service should be free from the desire for any material benefit or for sense gratification, as these desires are cultivated through fruitive activities and philosophical speculation. Generally, people are engaged in different activities to get some material profit, while most philosophers are engaged in proposing transcendental realization through volumes of word jugglery and speculation. Pure devotional service must always be free from such fruitive activities and philosophical speculations. One has to learn Kṛṣṇa consciousness or pure devotional service from the authorities by spontaneous loving service.
This devotional service is a sort of cultivation. It is not simply inaction for people who like to be inactive or devote their time to silent meditation. There are many different methods for people who want this, but cultivation of Kṛṣṇa consciousness is different. The particular word used by Śrīla Rūpa Gosvāmī in this connection is anuśīlana, or cultivation by following the predecessor teachers (ācāryas). As soon as we say "cultivation," we must refer to activity. Without activity, consciousness alone cannot help us. All activities may be divided into two classes: one class may be for achieving a certain goal, and the other may be for avoiding some unfavorable circumstance. In Sanskrit, these activities are called pravṛtti and nivṛtti—positive and negative action. There are many examples of negative action. For instance, a diseased person has to be cautious and take medicine in order to avoid some unfavorable illness.
Those who are cultivating spiritual life and executing devotional service are always engaged in activity. Such activity can be performed with the body or with the mind. Thinking, feeling and willing are all activities of the mind, and when we will to do something, the activity comes to be manifest by the gross bodily senses. Thus, in our mental activities we should always try to think of Kṛṣṇa and try to plan how to please Him, following in the footsteps of the great ācāryas and the personal spiritual master. There are activities of the body, activities of the different senses and activities of speech. A Kṛṣṇa conscious person engages his words in preaching the glories of the Lord. This is called kīrtana. And by his mind a Kṛṣṇa conscious person always thinks of the activities of the Lord—as He is speaking on the battlefield of Kurukṣetra or engaging in His various pastimes at Vṛndāvana with His devotees. In this way one can always think of the activities and pastimes of the Lord. This is the mental culture of Kṛṣṇa consciousness.