I would also recommend buying a planner so you can mark out your exams in advance. By scheduling out your exams, you can better plan for when you should start studying. Depending on the material, you can decide if you need weeks to study or days. I'm not much of a crammer, so I liked to give myself plenty of time. In doing so, I was able to master small portions of material at a time - much easier than trying to learn everything at once.
Along that line of thought, try to stay up to date with the material being taught in class. That means doing the reading when assigned and asking questions in class along the way. It can be easy to get behind but try to prioritize classes based on what you feel the most comfortable in. If you're great in one area, you probably need a little less time to get caught up than with a subject you have a little more difficulty in.
It's a balancing act that can take some time to get a feel for, but it gets easier with practice!
Best of luck!