As best you can, block time for class study. Designate times for each course. The normal rule of thumb is two hours of study for each hour of class. Schedule study sessions for time periods when you are most alert and productive. In general, avoid late night study.
Mornings are often productive time slots.
Unfortunately, we often dawdle during our most productive work periods. Be flexible - but not too flexible. If you are always changing your schedule, you need to analyze, prioritize and reschedule your activities. If your study environment has too many distractions, find a new one. Talk to friends about your schedule so that they are aware of your study - work hours.