This is not comprehensive but something on the top of my head:
Do's:
-get your stuff in early (application, letters of rec, essay, etc).
-carefully and thoroughly write and rewrite your personal statement. I cannot stress how important this essay is, especially with schools whose secondaries are just contact questions and request for money.
-let someone edit or proofread your personal statement. But don't let them make drastic changes to the content, especially if it concerns personal matters. Only you can know yourself best.
-write a letter of intent to a school that you kow you will definitely go if you are accepted.
-apply to schools that are "out of your league". Considering how random this process is, you'll never know.
-Make sure that everything on your online AMCAS application is accurate.
-Make sure AMCAS submits your application properly.
-if you can, make your secondary responses more personal.
Don'ts:
-turn in anything late.
-hassle the admissions office people. They have a lot of power
-list things that you are already present on your primary application in your secondaries.
-let your college premed counselor take control of your application. As in my case, my counselors don't know diddly squat what they are talking about.