Check out the old AMCAS application and get an idea of what you'll need to fill it out in a balanced way. If you fill anything in to see how it works, most of it won't remain when the new form comes out in May.
Collect "Contact" information for each activity you plan to list.
Definitely agree with this.
If you haven't already, get together a list of professors you're going to request LORs from and get in touch with them as soon as you get back from your winter break. I would recommend giving each recommender an "info" packet: a copy of your transcript, a copy of your personal statement, and perhaps a list of your ECs (or a CV if you have one). I think professors generally appreciate this and may lead to a stronger letter.
At least get started on your personal statement. You don't need to have a final draft ready to go, but a working draft would definitely be helpful. Some professors might even request a copy of your personal statement if they agree to write a letter for you. I also find it extremely helpful to take some time away from your PS, let it sit, and then come back and revise it as necessary. Getting a fresh look, IMO, results in better, more effective revisions.
Either informally (i.e., in your head) or formally (i.e., on paper), start going through the activities you've done and determining which ones you'd like to list on the application. For each activity, figure out why that activity was important to you. Why did you do it? What was most meaningful? Ideally you should be able to connect SOMETHING about that activity to your future role as a physician, but you may not be able to do that with every activity. Personally I find that activity descriptions are one of the most, if not the most, critical aspect of the application: through your activities I really get a sense of who you are and what makes you tick (something that isn't really visible in the PS or your grades).
Start working on picking the list of schools you're going to apply to. Get a copy of the MSAR and spend some time while watching TV and flip through it. Mark schools you're interested in AND ones at which your numbers will be competitive (if you don't have your MCAT score yet, use a conservative estimate of your score). If you have a very competitive application (i.e., strong numbers, expecting great LORs, great activities, etc.), you can probably get away with 10-15 schools; if your application is weak, you'll probably want to go with more and/or apply to less competitive schools.
You have plenty of time before the application opens so there's no need to be stressed, but the more prepared you are come May or June, the better.
