I am proof that it is not necessary to know anything in order to do well on MCAT
It is definitely possible to be a good test-taker.
Some things I've picked up:
1) An ounce of balls is worth a pound of competence. Walk in *knowing* that you will whup some MCAT and send it whimpering home to its momma.
2) Remember, the test-makers have handed you a sheet with all the correct answers on it. Think of it like a game of hide-and-seek. (Heeere, answer answer...)
2b) Would they really say that about [minority]? Dirty extremists! (Get rid of that choice.)
2c) "Wait, that's not physically possible..." Get rid of that one too.
2d) If you're really hosed, pick the answer that looks most like the others. Especially in PS.
3) On comprehensive tests, there are always long chains of related questions. Even if you know nothing about the topic, logical consistency often requires that the whole set work out in one particular way. I probably saved myself 2-3 PS points that way last August.
4) First principles are your friend. Don't be afraid to push electrons, know thy latin/greek.. and when in doubt, it increases surface area. Remember this, and you will never get an MCAT question you know nothing about.
5) If you're going to sit on a desk chair until your a$$ is chemically bound to it, you have to go prepared. I always bring a bag of bagels and a (small!) bottle of homemade iced tea.
6) If you find yourself talking yourself out of an answer for no other reason than your own paranoia, smack yourself immediately, or smack yourself later while checking your answers at home.
Hm...that's all I can think of for now. I agree with the people who push practice tests though. Test-taking is a skill, and it needs practice.
Avoiding work as usual,
Sunflower