(Click to enlarge photo of Srila Prabhupada and disciples, Bhaktivedanta Manor, 1973)
"The disciple must have the following qualifications. He must give up interest in the material bodily conception. He must give up material lust, anger, greed, illusion, madness and envy. He should be interested only in understanding the science of God, and he should be ready to consider all points in this matter. He should no longer think, 'I am this body,' or, 'This thing belongs to me.' One must love the spiritual master with unflinching faith, and one must be very steady and fixed. The bona fide disciple should be inquisitive to understand transcendental subject matter. He must not search out faults among good qualities, and he should no longer be interested in material topics. His only interest should be Kṛṣṇa, the Supreme Personality of Godhead.
As far as the mutual testing of the spiritual master and disciple is concerned, Śrīla Bhaktisiddhānta Sarasvatī Ṭhākura explains that a bona fide disciple must be very inquisitive to understand the transcendental subject matter. As stated in Śrīmad-Bhāgavatam (11.3.21):
tasmād guruṁ prapadyeta
jijñāsuḥ śreya uttamam
'One who is inquisitive to understand the highest goal and benefit of life must approach a bona fide spiritual master and surrender unto him.' A serious disciple must be alert when selecting a bona fide spiritual master. He must be sure that the spiritual master can deliver all the transcendental necessities. The spiritual master must observe how inquisitive the disciple is and how eager he is to understand the transcendental subject matter."
(Caitanya-caritāmṛta Madhya 24.330, Purport)