Well, I guess the first thing to do would be to check and see if there is a recommended dress code at all. Most dances our area college crowd attend don't have one so we go for "casual, but nice", but once in a while there will be a special even that asks people to dress up a bit more. I'd say exactly what you wear isn't too important as long as you like it, look good in it, and you're able to dance well in it (can move well in it). For example, in standard/smooth dances like foxtrot, waltz, and tango, one of your partner's legs will step/move in between both of yours, so you don't want to wear something that's going to restrict that movement. Of course you don't want to restrict your own leg movement either. A short, tight skirt probably won't work well, but neither would a long, floor length skirt that doesn't allow your legs a full range of motion. Something in the middle (length and/or closeness of fit) would probably be fine though. Men typically just wear a dress pants/shirt or a nice pants/shirt pair while women wear a variety of outfits -- dresses, skirt/blouse, pants/shirt, a sort of one piece pant suit, etc. As I said, I think that if you go for an outfit you like, that you look good in and can move well in so your dancing won't be restricted, you should be fine. Perhaps some of the women who read the board can give you additional suggestions -- dressing for men is often pretty simple, but women seem to have way more options making things more complex for them. I hope this helps though.
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James Marshall
marshall@astro.umd.edu http://www.astro.umd.edu/~marshall 
