submit your amcas (primary, on-line) application by mid-june. you will then start receiving secondary apps in july; have them done by mid-august. this is the absolute earliest and thus, the best way to handle your apps.
in order to submit your amcas application in june, ask for you letters of rec super early - like november of the year before! then schedule a meeting with your premed advisor to talk about your cover letter sometime in april. letters of recommendation is what can seriously hold your app back.
also, start drafts of your personal statement that january - write it over a few times. this can also hold you app back. just filling out your app you can do on the spot. you have access to the amcas primary app like in may or something - check it out and start filling it out early.
mcats: take it in april so that the scores are in by june so your file will be complete. if you take it in august, your file may not be looked at until the scores are in in october (not bad, but not ideal).
seriously, getting your app in on time is the most underestimated part of the process. I think late august, early september is problem the only time when med schools are not inundated with apps - after that, they start flowing in like crazy.
good luck with everything.
