1) Go to sleep before midnight, no matter what. If you still have work to do/things to study then make a plan to wake up a few hours earlier than normal. When you get up, eat, hop in the shower, then get to it. There were plenty of times last semester I was up at 3:30-4:00 studying and writing papers. I truly believe sleeping helped.
2) Eat well! but don't gorge yourself. It is difficult to focus when you are empty/stuffed.
3) Plan, Plan, Plan. You plan your workout routine, take at least that much effort in planning your studying. Stay on top of homework/reading. If you pay attention in/out of class, you really only need about a two week lead out from a test to prepare well. This doesn't mean you are slacking the rest of the time, it means you are busting your ass to get assignments done.
4) Study in blocks. Everyone is different, so the size of your block might not be the same as mine, and mine vary slightly week to week. After a few hours, when you feel your concentration failing, immediately get up and put the books aside (this amount of time is a block). Take an hour break to eat/watch tv/hit the gym/do cardio (you are unaware of the passage of time while sleeping so it doesnt work as well).
When you get back to it you will be able to maintain a higher level of concentration for almost as long. There is absolutely no point in studying if you are unable to concentrate, you will retain nothing and might as well stop there. My typical study block is about 3-3.5 hours. As the semester gets rolling, I usually do 4-6 hours/day (up to 10 approaching finals)
5) Never plan to study/work more than 7 hours/day. The last few are the least productive, and you might need more than you think you do anyway. If you think you need 10, you probably need 14.
6) if you can afford to when nearing finals, take every fourth day or so off or reduce the amount of work you do . This is only if you feel yourself burning out; I need to do this at times just to keep my sanity.
7) this is not for everyone by any means, but I found living with my gf to help a good deal. If I hadn't, I probably would have never had any time to see her. Making time to do so would have been fairly detrimental, as she occupies a lot of time
These are my tips, your individual study procedures really depend on how you learn best; people are too individual to prescribe a particular protocol. The above worked very well for me, I have a 3.9 (4.0 upper division GPA) in Mechanical Engineering (going into my senior year)while following pre-med coursework.