As someone who went through this: interviews go fast. Set your phone to alert you, contact programs as fast as they send out interviews, and keep a readily accessible list on Evernote or Google Docs so when you contact them you have 2-3 dates available in the ones they've offered, 2-3 they may say 'that's filled up' and you can't go searching right then on the phone, have a backup plan. One program kept filling up and I never got an interview, this was due to my priority with that program and my available dates, that is I didn't want to give up dates that I already made. If you give a date to a program and then attempt to contact them to change it you will be given what's left, i.e. not that much, so you have to prioritize.
If you're in a rotation, just say 'excuse me I was contacted about an interview' the residents will understand and at this point you're not getting letters of recommendation or evaluations on your profile
In general you receive a the large majority in Oct/Nov, then some may come in December. By mid-November I received about 80% of my total interviews and I went on 16 (which was overboard now that I look back). You will receive a wave in the first 3 weeks after the deans letter goes out, these are places that screen based on step 1 scores (they don't all read your personal statements).
Always, always have at least 18-24 hours between interviews, get your suit pressed, shirt ironed and get good sleep.
When you should contact programs: I did it twice, the best time is in mid/begining-december, this is when people credit cards bills are stacking up and travel plans are just not becoming realistic. I got offered two interviews this way, one offered me one date and the other offered me two dates, I scheduled one but got snowed out and it was their last date.
Don't contact programs in September/October and say 'I really want to go here, just so you know' if that was the the case you should've done an away there, otherwise it just seems like you probably sent that to everyone.
Another note: one or two places have people on the interview committee that come to your dinner the night before (wake forest) so act professionally at all times. Also ask where they do their rotations, some 'name' brand programs send you to different hospitals for things they are either deficient in or for intra-hospital political reasons they don't rotate in, usually happens for trauma or OB, to me this was a bad sign because it meant the department didn't have any clout in the hospital and it means you have to travel, something you won't appreciate the hassle of until you're in residency
Any questions you can PM me or ask, I'll be glad to answer from experience, just remember I'm only one person and other people will have different advice.
Best advice I got: get a credit card with a 1 year no interest if mom and dad aren't helping, get a good U-pillow for plane rides, that was indispensable.