Śrīla Rūpa Gosvāmī has given directions, in his Bhakti-rasāmṛta-sindhu, on how to accept a bona fide spiritual master and how to deal with him. First, the desiring candidate must find a bona fide spiritual master, and then he must very eagerly receive instructions from him and execute them. This is reciprocal service. A bona fide spiritual master or saintly person always desires to elevate a common man who comes to him. Because everyone is under the delusion of māyā and is forgetful of his prime duty, Kṛṣṇa consciousness, a saintly person always desires that everyone become a saintly person. It is the function of a saintly person to invoke Kṛṣṇa consciousness in every forgetful common man.
Manu said that since he was advised and instructed by Kardama Muni, he was very much favored. He considered himself lucky to receive the message by aural reception. It is especially mentioned here that one should be very inquisitive to hear with open ears from the authorized source of the bona fide spiritual master. How is one to receive? One should receive the transcendental message by aural reception. The word karṇa-randhraiḥ means "through the holes of the ears." The favor of the spiritual master is not received through any other part of the body but the ears. This does not mean, however, that the spiritual master gives a particular type of mantra through the ears in exchange for some dollars and if the man meditates on that he achieves perfection and becomes God within six months. Such reception through the ears is bogus. The real fact is that a bona fide spiritual master knows the nature of a particular man and what sort of duties he can perform in Kṛṣṇa consciousness, and he instructs him in that way. He instructs him through the ear, not privately, but publicly. "You are fit for such and such work in Kṛṣṇa consciousness. You can act in this way." One person is advised to act in Kṛṣṇa consciousness by working in the Deities' room, another is advised to act in Kṛṣṇa consciousness by performing editorial work, another is advised to do preaching work, and another is advised to carry out Kṛṣṇa consciousness in the cooking department. There are different departments of activity in Kṛṣṇa consciousness, and a spiritual master, knowing the particular ability of a particular man, trains him in such a way that by his tendency to act he becomes perfect. Bhagavad-gītā makes it clear that one can attain the highest perfection of spiritual life simply by offering service according to his ability, just as Arjuna served Kṛṣṇa by his ability in the military art. Arjuna offered his service fully as a military man, and he became perfect. Similarly, an artist can attain perfection simply by performing artistic work under the direction of the spiritual master. If one is a literary man, he can write articles and poetry for the service of the Lord under the direction of the spiritual master. One has to receive the message of the spiritual master regarding how to act in one's capacity, for the spiritual master is expert in giving such instructions.
This combination, the instruction of the spiritual master and the faithful execution of the instruction by the disciple, makes the entire process perfect. Śrīla Viśvanātha Cakravartī Ṭhākura describes in his explanation of the verse in Bhagavad-gītā, vyavasāyātmikā buddhiḥ, that one who wants to be certain to achieve spiritual success must take the instruction from the spiritual master as to what his particular function is. He should faithfully try to execute that particular instruction and should consider that his life and soul. The faithful execution of the instruction which he receives from the spiritual master is the only duty of a disciple, and that will bring him perfection. One should be very careful to receive the message from the spiritual master through the ears and execute it faithfully. That will make one's life successful.