Please consult a real yogasana guru who can teach you practically. I feel it is not the right way you want to receive the gyana. You might have gone through the books and videos also said about these Bandha therein but ultimately you are seeking for a guide from a human guru then tell me what the use of these books and CDs?
I can only tell you please go to real Yogasram where you can receive such valuable gyana instead seeking for a guidance in media if you really want Yoga in your life.
If you really want to know about the bandhas, then you can read the blog which is best for you to know about Bandhas. In Yoga Teacher Training in India you will learn the Bandhas aspects from the qualified yoga instructor.