I'm similar to tendram in the sense that it depends on the class. For anything math related (math, physics, pchem), I do practice problems. For more conceptual things like Chem, or mainly biology, I take sloppy, quick notes on loose sheets of paper in class and go home and rewrite them neatly in a spiral notebook. I use the textbook or the internet to fill in knowledge gaps when I'm rewriting (never read the textbook before going to class). For exams and quizzes, I review my rewritten notes out loud.