Srila Prabhupada- Lord Caitanya said that whether one is brahmana or whatever he may be if he knows the science of Krsna then he is to be accepted as guru. So one who gives class , he must read and study regularly and study the purport and realize it . Don’t add anything or concoct anything, then he can preach very nicely. The qualification for leading (the) class is how much one understands about Krsna and surrendering to the process .

(Letter to Malati  —  Bombay 25 December, 1974)