Therefore the beginning of spiritual education is to understand one’s self. That is called self-realization. How to realize the self? We have to take knowledge from others. We have to learn from a teacher. Krishna is accepted as the supreme teacher by great sages like Vyasadeva, Narada, Devala, Asita, and all other great sages, and in the modern age by our acharyas, spiritual preceptors: Ramanujacharya, Madhvacharya, Vishnusvami, Nimbarka, Shankaracharya. We have to follow the acharyas. All these acharyas accept Krishna as the Supreme Lord. And five hundred years ago Sri Chaitanya Mahaprabhu also accepted Krishna as the Supreme Personality of Godhead
ISKCON/ Hare Krishna Movement initiates vow not to participate in : “No intoxication , including coffee or tea ” as well as no gambling , meat eating or illicit sex. These are considered sinful activities that prolong our stay in the material world and contribute to repeated reincarnation. They are an impediment to developing pure love for God / Krishna
The guys who may have taken drugs previous to becoming devotees, could back-slide into that practice if they do not have good association to remain spiritually strong. Those who are envious of the Hare Krishna Movement will look for any flaws they can find, real or imagined.
Bhagavad-gita is the science of understanding God. As everything is understood thoroughly through a scientific process, if you want to know God you have to adopt the process by which one can understand God. That process is described in the Bhagavad-gita: bhaktya mam abhijanati. Krishna, the Supreme Personality of Godhead, says, “If anyone wants to understand Me, he has to take to the process of devotional service,” not the speculative process or the mystic yogic process or fruitive activities.