AP classes are great ways to get college credit if you do well on the CLEP exam. Just like other classes, though, mastery depends on the class, not the test. If a class teaches toward doing well on the CLEP, you may get good test scores but don't really know how it all works. For example, in my physics classes, my biggest task is to get students to stop searching for the formula in the book, and learn how to build their own. This is even more true for students who took AP Physics and spent all their time doing nothing but problems.
Best ways to succeed in college:
1) Read ahead at least three class sessions, so you know what's going on when you walk in.
2) Take notes while you read, take notes in lecture, take notes while you do homework--and rewrite your notes after!
3) Start your homework on the day it's assigned. That gives you time to break up assignments into manageable tasks, and to get help when you run into trouble.
4) You will run into trouble! Go see the instructor as soon as you have questions. Don't wait until the night before a test. See the instructor at least once a week, just to make sure you're on track.
There are lots of other hints, but this is a good start! Good luck.