“There are ten meanings for the word "bhakti" ("devotional service"). One is sādhana-bhakti, execution of devotional service according to the regulative principles, and the other nine are varieties of prema-bhakti, ecstatic love of Godhead.

The nine varieties of prema-bhakti are rati, prema, sneha, māna, praṇaya, rāga, anurāga, bhāva and mahābhāva—attraction, love, affection, adverse feelings, intimacy, attachment, subattachment, ecstatic love and sublime ecstatic love. For the word sādhana-bhakti there is only one meaning, "the execution of devotional service according to regulative principles."
(Sri Caitanya Caritamrta--2:24:30--translation and purport).

The next set of instructions is listed as follows:
(1) One should rigidly give up the company of nondevotees.
(2) One should not instruct a person who is not desirous of accepting devotional service.
(3) One should not be very enthusiastic about constructing costly temples or monasteries.
(4) One should not try to read too many books, nor should one develop the idea of earning his livelihood by lecturing on or professionally reciting Śrīmad-Bhāgavatam or Bhagavad-gītā.
(5) One should not be neglectful in ordinary dealings.
(6) One should not be under the spell of lamentation in loss or jubilation in gain.
(7) One should not disrespect the demigods.
(8) One should not give unnecessary trouble to any living entity.
(9) One should carefully avoid the various offenses in chanting the holy name of the Lord or in worshiping the Deity in the temple.
(10) One should be very intolerant toward the blasphemy of the Supreme Personality of Godhead, Kṛṣṇa, or His devotees.

Without following the above-mentioned ten principles, one cannot properly elevate himself to the platform of sādhana-bhakti, or devotional service in practice. Altogether, Śrīla Rūpa Gosvāmī mentions twenty items, and all of them are very important. Out of the twenty, the first three—namely accepting the shelter of a bona fide spiritual master, taking initiation from him and serving him with respect and reverence—are the most important.
(Nectar of Devotion).

At this point, Śrī Caitanya Mahāprabhu replied, "This is all right, but still you can speak more on the subject."
Rāmānanda Rāya then replied, "Ecstatic love for the Supreme Personality of Godhead is the essence of all perfection."

In his Amṛta-pravāha-bhāṣya, Śrīla Bhaktivinoda Ṭhākura summarizes the conversation up to this point, where Lord Caitanya Mahāprabhu says to Rāmānanda Rāya, eho haya, āge kaha āra: "This is the process accepted in devotional service, but there is something more than this. Therefore please explain what is beyond." Simply executing the duties of all varṇas and āśramas is not as good as offering all the results of one's activities to the Lord. When one gives up all fruitive activity and fully surrenders to the Lord, he attains sva-dharma-tyāga, wherein he abandons the social order and takes to the renounced order. That is certainly better. However, better than the renounced order is cultivation of knowledge mixed with devotional service. Yet all these activities are external to the activities of the spiritual world. There is no touch of pure devotional service in them. Pure devotional service cannot be attained by empiric philosophy, nor can perfection be attained simply by good association. Devotional service by self-realization is a different subject matter. It is untouched by fruitive activity, for one surrenders the results of activities to the Lord, abandons prescribed duties and accepts the renounced order of life. Such devotional service is situated on a higher platform than that of empiric philosophical speculation with a mixture of bhakti. This is verified by Śrīla Rūpa Gosvāmī in his Bhakti-rasāmṛta-sindhu (1.1.11):

anyābhilāṣitā-śūnyaṁ jñāna-karmādy-anāvṛtam
ānukūlyena kṛṣṇānu-śīlanaṁ bhaktir uttamā
(CC-2:19:167))

"One should render transcendental loving service to the Supreme Lord Kṛṣṇa favorably and without desire for material profit or gain through fruitive activities or philosophical speculation. That is called pure devotional service."

Devotional activities, however, sometimes appear to be impure in the neophyte stage, but in the mature stage they are completely pure, or free from material activity. Therefore Rāmānanda Rāya replied after hearing the last statement of Śrī Caitanya Mahāprabhu: prema-bhakti—sarva-sādhya-sāra. Śrī Caitanya Mahāprabhu actually accepted this verse (jñāne prayāsam) as the basic principle of perfection. One has to practice this principle in order to make further progress. When further progress is actually made, one comes to the platform of ecstatic loving service to the Lord. This first stage is technically called sādhana-bhakti, or devotional service in practice. The result of sādhana-bhakti must be ecstatic love, attachment for the Supreme Personality of Godhead, which is also called prema-bhakti. In the neophyte stage, sādhana-bhakti includes faith, association with devotees, and practicing devotional service. Thus one is freed from all unwanted things. One then becomes fixed in devotional service and increases his desire to act in devotional service. Thus one becomes attached to the Lord and His devotional service.
(Sri Caitanya Caritamrta-2:8:68--translation and purport).