The MCAT is not the kind of exam you can ace with an all-night cram session. You'll need at least three months of preparation, and that time should be used wisely. Sit down as soon as you can and draw up a step-by-step study plan. Make a promise to yourself that you'll follow it meticulously. Figure out what you'll need to review, what materials you'll require, who will be in your study group, what kinds of practice tests you'll need to take and whether you'll need any remedial assistance, such as a speed-reading clinic offered by your college guidance program.
Also, get a daily calendar (or use the calendar function in your phone) and block out exactly when you're going to do your prep sessions. Set aside time for healthy meals and an exercise regimen, too.
"School is a full-time job," notes William J. Rapaport of the University of Buffalo. "And managing your time is important.... Your education should come first" [source: Rapaport]. Look at the MCAT in similar fashion: It's a test, it's a course, it's a full-time job.