I think this could be a helpful thread - as long as it doesn't become a way for people to take out personal bitterness against programs. In order words, it would help if everyone were objective.
In general, there are a few tips that, if not adhered to, could create a "mistake".
1. Realize that your best interview will be the last one of the season. You get better with each one and you get more comfortable with the format and even anticipating some of the odd-ball questions. Thus, you come across as a more confident individual as the interview season ends. Therefore, if you have any say in it, try to schedule your favorite programs for later in the cycle. But, do NOT make the mistake of viewing your first interviews as "trial runs". This is ortho - there are no trial runs. Hopefully, you also recognize from this advice that doing aways at programs that interview you while you're rotating may not be a great thing.
2. There are NO second rate programs in ortho! Cherish each interview and make up your mind that you're going to do your best no matter what you think of the program/location going in. If you don't think you'd rank a program, do everyone else a favor and DON'T APPLY or at least don't accept the offer to interview.
3. Go to the pre-interview dinners. If you didn't rotate at a program, this may be the only way they have to get to know what kind of person you are. It's also your chance to see them in a relaxed setting. I'm a major introvert and hated those things, but put your game face on and view it as part of the interview (because it certainly is no matter what they say). Be ready to ask intelligent (but not dorky) questions that show you've thought about the program. If you come from a great school or did great on the boards or are junior AOA, don't bring it up - they can read your file and they're not that impressed. The school name on your diploma won't get you a residency.
4. Realize that aways are two edged sword. They can make you look good if you can keep up a strong front to EVERY resident and attending for four weeks. But, all it takes is screwing up or making even one guy not like you to ruin the entire rotation.
Good luck to everyone!