First off, yes, read the bible.
Secondly, don't feel you have to be one of those loud jack-offs constantly yelling stupid remarks in class or trying to be EVERYBODY'S friend. It's amusing for a while, but quickly becomes very old.
Just focus on actually doing the work your supposed to be doing (afterall that is why your there), and if there's any hotties or any of your buds in your class, just chat with them. You say it's easy for you to talk with your friends about anything, so that solves half your problem right there. And as far as chatting up hot babes, that will probably make you nervous for now. GOOD. Read the bible, apply what you learn. You'll f*ck up at first, but you'll gain experience, and slowly but surely you will become a macking machine. The more experience you gain, the more your confidence will go up, and then talking to those jerks in your classes will be easy as pie.