24f, Applying my second time.
Biggest lessons I have learned is to 1) Fill out AMCAS thoroughly (i.e. don't just leave off activities because you didn't think they were that important) and 2) (everyone should agree) APPLY EARLY (i.e. submit AMCAS in June, turn secondaries around in <1 week).
Man, those were some expensive lessons to learn. Last year, no acceptances. This year, applied early and already have 3. Go figure.
Though, I really do feel that part of this admissions process is luck. Which I guess leads me to point 3) after you submit your secondaries, aside from a LOI (interest or intent) there's not much more that you can do, so relax and try to breathe!
Get it right the first time, because unless you come from money (or mommy and daddy are willing to cough up money), the bill for all this is a pain in the rear! Not something you really want to struggle with twice (or more)...