I just wanted to interject that the MCAT is NOT the most important part of your application! Being a well-rounded person with significant life experiences that will help you become a compassionate and competent physician is key. Grades and MCAT scores simply show that a person is academically prepared to do well in coursework and the boards.
I personally know someone who got somewhere in the neighborhood of a 40 on the MCAT (she smoked it) and a 4.0 coming out of the honors college at my university. Very little clinical experience and/or volunteer work. Even with these stellar stats, she was rejected from all of her dream schools, and was only waitlisted at the state school. Eventually she got in off of the waitlist, and is now kicking serious butt in med school classes, but it just goes to show that scores/grades are certainly not everything.
If you really want to start preparing yourself for the MCAT, look into the AAMC literature on the MCAT: <a href="http://www.aamc.org/students/mcat/start.htm" target="_blank">http://www.aamc.org/students/mcat/start.htm</a>
Print out the MCAT Student Manual from this website, and it will give you the specific items from your premed coursework that you will be responsible for, which can help you direct your early studying for the test. This page will also give you information about future changes to the MCAT. For instance, at the bottom of the webpage, it lists minor changes for the 2003 MCAT. Expect even more changes for the 2004 and beyond MCATs.
Good luck, and don't stress out about the test until you really need to. Right now concentrate on your current coursework and really just being a college student. Have fun in college, but don't forget to gain important clinical and/or volunteer experience, and possibly some leadership and research experience along the way. Chill, and have a great college experience. Stressing about med school and the application process will come in time. Stressing while you are in med school and in residency will also come before you know it. Take time now while you have it to just really live life and enjoy it. I know college can also be stressful, but right now is one of the few chances you will have to not have enormous responsibilities, debt, and stress hanging over your head. Again, have fun and live life while you can.
Sorry for my ramblings. Good luck.