When can you start filling out the application? Can I start now to fil them out and then just hit send on the first day that applications can be sent?
For AMCAS you have to wait until may(ish) before the application for 2005/2006 open. Then you can submit early june. If you absolutely cannot wait and must start, work on your personal statement and 2-3 sentence descriptions of no more than 15 “activities” including work experience. Also, mid-March, start requesting unofficial of your transcripts so they are in your hands when the app cycle opens. Finally, have your official transcripts sent the day the cycle opens and be obsessive about their arrival. This will give you a healthy jump on the process next year. Hope that helps!
If you think you have a good chance of getting into AMCAS schools and might prefer those, then I strongly advise waiting to submit your AACOMAS. Otherwise, DO schools will interview you, accept you, and ask you for a nonrefundable seat deposit ($500, $1000, $2000) before you have even heard from the MD schools.
I sent in my AMCAS in June and AACOMAS in October and the timing was pretty good. I only lost $500 on one DO seat deposit.
Also, get going on your personal statement now. It can take a long time to produce a good one (which is essential), and you will need to provide it to whomever is writing letters of reference for you. Other prep things are requesting your transcripts and figuring out how you are going to handle your LORs. I had very good results with the premed office at the university where I took my prereqs; they collected and sent out all my LORs, which saved me and my referees a lot of trouble.