Here's my strategy for avoiding burnout, and this comes from a guy who's made his fair share of mistakes in school:
Step 1:
RateMyProfessor.com
Find the professors that provide in-class note packets and that students generally regard as having interesting lectures that cover the scope of the material. I've gotten A's in many classes without ever having to open my book because the professor provided excellent notes and explained things well. A good teacher is invaluable and can eliminate a lot of unnecessary studying which means less burnout.
Step 2:
Make sure you get enough sleep for you. Most people don't remember jack if they're running off of 6 hours or less, so if you go to class all tired, unless you're a stud, you're going to be up late studying. It turns into a viscious cycle fast.
Step 3:
Class time is sacred. When you're in class, avoid daydreaming at all costs and make sure to write down little bits of information that are key during the class, even if its sole purpose is to make sure you're paying attention. Caffeine is optional. Never miss any classes if you can avoid it.
Step 4:
NEVER procrastinate. Cramming sucks and countless studies show that you forget the information quickly. Remember that your MCATs are going to be over all the information you've accumulated in Math, Physics, Biology and Chemistry, so it's best to have it lodged in your head by learning it the right way rather than just for the exam. The earlier you start, the less pressured you are to finish and the more likely you are to actually get it done. For a lot of people, if something seems insurmountable, their brain says, "What's the use, why try?" but if it seems within their reach, the brain is thinking, "I can do this, I'm excited to finish this and get it over with."
Other personal preferences:
Shorter classes and more of them. Anything over 50 minutes kills my attention span, and having more than 4 hours in a single day starts to get old. I like MTWRF classes for 5 credit hour courses whenever possible.
Taking breaks. Internet, Scrubs, Porn, anything that makes me happy. Unless I'm writing a paper (I have an unnatural love for writing, if you haven't noticed), I like to hit something hard for about 30 minutes to an hour and then take a while to relax.
Summer Classes. It gets a lot of stuff out of the way quickly so that you can further structure your semesters for success. Nothing like a 12-hour semester near the end of your college to help you take it easy.
I've already charted out what my semesters will look like in the future, and while it will change, those summer courses have given me a ton of flexibility hour-wise.
