On account of his association with mahātmās, or great souls one hundred percent in the devotional service of the Lord, one may attain a little bit of attraction for Śrī Kṛṣṇa. But at the same time one may remain very much attached to fruitive activities and material sense enjoyment and not be prepared to undergo the different types of renunciation. Such a person, if he has unflinching attraction to Kṛṣṇa, becomes an eligible candidate for discharging devotional service.
This attraction for Kṛṣṇa consciousness in association with pure devotees is the sign of great fortune. It is confirmed by Lord Caitanya that only the fortunate persons, by the mercy of both a bona fide spiritual master and Kṛṣṇa, will get the seed of devotional service. In this connection, Lord Kṛṣṇa says in Śrīmad-Bhāgavatam, Eleventh Canto, 20th Chapter, verse 8: "My dear Uddhava, only by exceptional fortune does someone become attracted to Me (Kṛṣṇa). And even if one is not completely detached from fruitive activities, or is not completely attached to devotional service, such service is quickly effective."
Devotees can be divided into three classes. The first or uppermost class is described as follows: one is very expert in the study of relevant scriptures, and he is also expert in putting forward arguments in terms of those scriptures. He can very nicely present conclusions with perfect discretion and can consider the ways of devotional service in a decisive way. He understands perfectly that the ultimate goal of life is to attain to the transcendental loving service of Kṛṣṇa, and he knows that Kṛṣṇa is the only object of worship and love. This first-class devotee is one who has strictly followed the rules and regulations under the training of a bona fide spiritual master and has sincerely obeyed him in accord with revealed scriptures. Thus being fully trained to preach and become a spiritual master himself, he is considered first-class. A first-class devotee never deviates from the principles of higher authority, and he attains firm faith in the scriptures by understanding with all reasons and arguments. When we speak of arguments and reason, it means arguments and reason on the basis of revealed scripture. The first-class devotee is not interested in dry speculative methods meant for wasting time. In other words, one who has attained a mature determination in the matter of devotional service can be accepted as the first-class devotee.