Prabhupada always used to emphasize that if you preach, everything else will come. In other words, if you are giving Krsna to others, if you are actually concerned about their spiritual welfare and want to see them advance in spiritual life, you do not have to worry because when you give Krsna to others, reciprocation naturally takes place.
Caitanya Caritamrita Lectures Book, Madhya Lila, Pg 307