Use the time on the weekends or holidays to continue to work ahead or to catch-up on work that you may have let slide in your other classes. Plan your study time. Typically, study for 50 minutes, then break for 10 min. Go for a cup of coffee or visit a friend down the hall during those 10 min. These incentives will help to keep you going.
Some people benefit from studying with a group of students, others prefer studying alone.
You should try both methods to find out which one benefits you the most. Plan to spend at least 2 nights studying for a major exam. Rather than high lighting several passages in the textbook, write notes or questions to yourself in the margins that will help strengthen your retention of material. Don't gorge on caffeinated beverages or foods in an effort to stay awake. You could end up jittery and nervous and unable to focus during the exam.