Wow, I forgot how early I got interested in rotations 🙂 OMS-II here. The link that kbeitz put down is a bit out of date. ESPECIALLY when it comes to AL rotations (for example). ACOM started their first rotational class this year, and I KNOW that the organization that has been running AL rotation sites for about 2 decades has ACOM as a main priority (right behind UAB and USA). Also, give it a couple years and the new DO school at Auburn (VCOM?) is going to crowd that system even more.
As far as rotations being "what you put into them"... absolutely SPOT ON. J-track (ATL rotational sites... ALL OVER Atlanta) can be somewhat unpredictable. I have known some 3rd years who have had very few to no changes. I know some that have had a couple changes and didn't take it well (they hadn't checked with the doctor until the week of the rotation) and lost time, having to rearrange the schedule to get any credit at all. I know some that had a couple changes, took advantage of what was available, and say they have had great experiences.
As far as what rotation YOU want to be in... according to multiple 4th year students (they held a Q&A session with video conferencing for distant sites), every site offers its own set of pro's and con's. You have to know what you want (a problem as you won't have experience yet), and where that would be best served (another problem since you won't have a clue what sites offer what). For instance, in that session several 4th years mentioned that more rural rotations usually give MUCH more leniency on what a student is allowed to do. One student mentioned that he was 1st assist in every surgery he observed and, specifically, within his first week of surgery rotation was holding 5 feet of bowel. They also mentioned that, when possible, you could try to get a rotation that has a residency program that you are interested in. I THINK they mentioned that Columbus has several residencies, but I was focused on a different track (Warner Robins) that has 1 residency that I am interested in. Having a residency director available in the field you are interested in is a great bonus because they all know each other, and they talk. So don't be an idiot, but that SHOULD go without saying 🙂
One mistake from kbeitz, though, is to wait until "you have made it through 2nd year and boards". The link says that you will get contacted mid-Fall term of 2nd year. It hasn't happened for us yet, but there has been talk. Experience from last year says that they submitted their personal "I want" lists towards the end of Oct and they knew by Thanksgiving what they had drawn. Then they had a time (I don't know how long, but not short enough to complain, and not long enough to interfere) to make trades. I WOULD say, however, to not worry about it until you make it through 1st year. At that point, you can try contacting folks during your summer to see if you can figure out what it is you want, and where that may be best offered.
Congrats on getting picked up. PCOM is a great institution, and a great family.