I'm not exactly sure, but I do know that the more you do and the more contacts you have, the easier it is.
After doing a couple of electives in the same place and building up a good relationship with the faculty you will probably be at least given an interview when it comes time for a residency and of course top scores on the USMLE will only help you.
Basically, you're headed in the right direction--just keep working hard and stick with it and I'm sure the sky's the limit!
