Krsna realization begins from the tongue. How? Now you simply make it a vow, that “I shall not accept anything that is not offered to Krsna.” And you take another vow, that “I shall not talk anything except glorifying the Lord.” Then you become perfect. Very simple method. Simply you have to make this determination, that “I shall not talk anything which is not about Krsna, and I shall not eat anything which is not offered to Krsna.”

From Srila Prabhupada’s lecture on, Bhagavad-gita 4.27 — April 16, 1974, Bombay.