Plan to study between classes. Most people can think more clearly during the day. Do assignments immediately after class, with the lecture still fresh in your mind. A review right before a test is an effective way to raise your grade because you refresh your short-term memory. Don't rob yourself of sleep.
Adequate sleep is just as important as studying for academic success.
Allow and use the time to get nutritious food and regular meals. Schedule some time for goofing off. If you have favorite TV programs, include them. Reward yourself with extra leisure time if you finish tasks on your time budget early. Allow time for exercise.