Before reading a chapter, survey it. Take five minutes to get the basic ideas and to form questions as you begin to read. Have a conversation with the author as you read. This technique ensures that you are involved with the subject matter. If you have an hour between classes, use it.
Scattered study is often better than concentrated study.
The more times you study something, the better you'll remember it. If you're having problems understanding a subject, get help immediately. Too often we hesitate to ask for help because we don't want to appear ignorant. Students often allow themselves to become distracted in class, either by the idiosyncrasies of the instructor or by somebody's purple tie. This cuts your listening efficiency, and listening is an important part of college.