Mantra for the Brahmachari

Namaste sir, I have been interacting with your good self and reading ur articles quite often and I really feel good to have your knowlegde and experience helping me and others, the questions are many times small and answers are very large and explanatory, I thanks for ur efforts, I understand that every has to make his efforts, I want to ask about mantras ie what mantras to chant in general, eg bij mantras, other basic mantras and where to concentrate, any good book or site for mantras for reference, I know that mantras carry energy but its a vast topic and I want ur guidance as basic level, may be for others who are beginners, , thanks and regards