Read the textbook before lecture so that during lecture, it's your second go-round and you internalize the material and grasp the subtleties. Most people hear the material for the first time during lecture, and miss the subtleties altogether.
Copy your lecture notes over neatly after lecture. You get another chance to carefully review the material that way and formulate questions for office hours.
Look at and try to figure out how to do every problem as soon as you get them, form questions and go to office hours. Most people wait until the last minute, and then office hours are not useful because you haven't formulated questions yet.
Prepare for exams by doing problem after problem after problem. Do problems that weren't assigned, use other textbooks, etc, but find more problems. Work in groups, but with people as dedicated as you. Avoid blind leading the blind situations. If your working with someone who is slacking and slowing you down, tell them to shape up or ship out. It's not personal, it's strictly business.
Get enough sleep.