Make sure you review slides/notes from your lectures. Try to solve at least some of the relevant textbook problems. Make sure you timely visit your professor/TA to ask for help on problems you can't solve. Frequently visiting your professor/TA is more important that you may realize.
I suppose when it comes down to it all, you have to work hard, timely submit your homework, and be prepared for your quizzes and exams. :) Common sense really!!!