Being an average applicant myself, hopefully I can shed some light/give some advice. I would definitely do away rotations if you don't plan on staying at your home school/feel like you don't have a good shot there. If you want to stay at home and feel like you have a good shot, they may not be necessary. If you do them, do them early, and get a letter (it looks good to have someone from another institution say something good about you).
I think the biggest mistake is choosing an away based on 'knowing someone there' or 'it's close to home.' Do a little research and find a place that you're really interested in, and that's in a location you want to be. Unless you're a total masochist, I'd also try to stay away from programs that take like 50 rotators (HSS, many of the Chicago schools, yada yada yada) unless you really want to go there. This was my strategy: do two aways, one at a program that you think might otherwise be out of your league, and one that is kind of a 'safety' school. I think this strategy worked out pretty well as I ended up with letters from both places - and it showed I was versatile in different learning environments.
I'll tell you this though... aways can either help you or hurt you - they are rarely neutral. You have to be on your game 100% of the time, and you have to kill the rotation for it to help you - there are many more ways for it to hurt you (someone not liking you, you getting burnt out, having a crappy resident, etc).
I hope that helps a little bit... good luck!