This is only the 2nd year they have used this system of scheduling clinics, so there really isn't a "normal" way of working. It has had some glitches, and I know they have improved it a TON since just last year, so I'm sure by the time you get there, it will be much more smooth 🙂
Anyway, a couple of months before you submit your requests for electives and such, you will hear about the electives from the clinicians who organize them. Some of them you can set up before the process of requesting electives and they'll just work around that when they schedule the rest of your rotations (lab animal comes to mind for one that we could set up beforehand). We were able to rank any of the electives we want, our other free block, and any of our required rotations.
For instance, I wanted the cardiology elective, but since it is competitive, I put it at the number 1 or 2 spot. Then I ranked my other off block to be at a specific time (I didn't get it but my schedule happened to work out so that I had free time when I wanted it anyway). Then I wanted a rotation that historically requires no weekend duty when I know one of my friends is getting married so I ranked some of the required rotations for those blocks and I ended up getting it.
They tried to get the computer to maximize all of our "happiness" (they related it to Sims lol), but the system was apparently really glitchy so they are going to have to go through add/drop requests by hand... which sucks for them.