If you're far away from it, DON'T START STUDYING FOR IT. Seriously, it won't do you any good and will just add stress. You should start studying for it about 3-5 months before you plan to take it, at most (even 4 months prior is pushing it). You don't need more time than that if you do it right. Trying to study for it before you've even taken the requisite classes is just stupid because you don't have the knowledge you need.
If you really want a leg up, start reading dense publications (like the Economist, or any scientific journal articles) and really try to comprehend them. The MCAT is more of a verbal comprehension and reasoning test than a knowledge test.
I took a Kaplan course for it; the classroom portion and their strategies were a waste of time. However, their practice material was well worth it. They had like 17 practice tests I think, and great science review.
The best way to study for it is to take as many practice tests as possible. Buy all 7 or whatever from the AAMC website for sure; they're $35 each I think but are worth more than all the other study material you could possibly find. As for what books to use, if you're not sure whether to get one prep book or another, it's a sign you should get both. Kaplan and Princeton are good (Kaplan verbal is crap though; don't use it for one second). I've also heard good things about Exam Krackers and Berkeley Review.
Again, if you're not even close to taking it, then don't even think about studying for it. There are better ways for you to spend your time. Hell, just have fun and do something you enjoy. Or study for your current classes, or anything really.