Anytime I think I will have trouble with a course I do this: I buy that courses textbook and if available solution guide months in advance. (You are going to purchase them anyways, so no monetary harm is done.) Then I read the text and work as many sample problems as I have time for (using the solution guide to check). By the time the class starts, I have a good background and can sit back and learn during the lecture instead of frantically trying to write down everything the lecturer says (meaning you aren't learning much, but just copying).
Some universities will let you take every course online.