How one can tell that he is a devotee of Krsna (one should hear about Krsna from Krsna devotee, not a professional man)?

Expressions researched:
"How one can tell that he is a devotee of Krsna"

Srimad-Bhagavatam Lectures

You have to see that by chanting Kṛṣṇa, what he is doing? He is maintaining his body, or he is actually desirous of advancing in Kṛṣṇa consciousness. That you have to know.

Lecture on SB 1.2.5 -- Vrndavana, October 16, 1972:

Indian: If hearing is more important than chanting, then from whom a man should hear about Kṛṣṇa? It is from anyone?

Prabhupāda: What is that question?

Devotee: He says hearing, hearing is more important...

Prabhupāda: Everything is more important, but hearing is especially given.

Indian: From whom one should hear about Kṛṣṇa?

Prabhupāda: From Kṛṣṇa devotee, not a professional man.

Indian: How one can tell that he is a devotee of Kṛṣṇa?

Prabhupāda: That requires little intelligence. One has to learn. It cannot be... You have to see that by chanting Kṛṣṇa, what he is doing? He is maintaining his body, or he is actually desirous of advancing in Kṛṣṇa consciousness. That you have to know. Chant. (end)