several things will determine where you end up applying to:
what are your qualifications/stats? how competitive of an applicant are you? (this requires an honest self-appraisal as well as appraisal from unbiased folks such as advisers)
do you have a geographical preference? would you rather stay on the east coast, midwest, or west coast? or are you pretty flexible?
do you want to go to a big institution with lots of research options or a smaller, cozier institutions with specific established strengths? (this requires a lot of research on your part...i didn't do this much when i was applying. i was too lazy.)
generally when you apply via AMCAS, it is advised to cast a wide net (i.e., apply to a lot of places). if you are an uber-candidate, you'll get interviews everywhere you apply. so if you checked off 20 schools on that little AMCAS form, you'll hear from all 20 at some point.
of course, you don't wanna be going to 20 interviews...that would be way too exhausting. if the less desirable programs for you invite you for interview first, schedule a few of them early but the others late. the early interviews will serve as a warmup so that you can see if you feel comfortable walking around in your interview suit and you get used to the whole interview/wine-n-dine routine. the late interviews are there as a backup but you can cancel them. eventually, your top choice programs will also invite you for interview. schedule those somewhere in the middle of your schedule.
feel free to PM me if you want more personalized advice.