You can generally ask anybody you want, even if you are very new, so don't be too shy. You'll see that it shakes out with folks tending to dance with people around their own level, but that is not a law, that's mainly less experienced folks being shy to ask more experienced dancers. While it is probably smart to not get too greedy with asking the best dancer 10 times in a row, it really is fine to ask someone better than you for a dance once in a while, it can be fun for both people.
Don't ask someone to dance by telling them how terrible you are. It's like when your friend says "man this food tastes horrible!" and then asks you to taste it. A bad sell. If you are a new dancer, it's no problem to mention it, but keep it positive & brief and get to the dancing. If you are nervous, that's all good, just be nervous and don't talk about it the whole dance and try to smile, it really goes a long way.
Don't apologize the entire dance. Everyone goofs up from time to time and it really is no big deal. Like many other interactions in life, the fun your partner has is based to a surprising degree on the fun you have, so try to relax and enjoy yourself.
For that matter feel no obligation to talk the entire dance. The great thing about social dancing is how you can communicate your response to the music without talking. You can introduce yourself etc, but if you have a conversation for the entire dance, you may miss some of the fun - and if you are new, talking and partnering at the same time can be tough!
Generally people say yes to a dance but of course, you can say no to whoever you want. If you do, just be nice about it, and if you are willing to dance later, maybe ask for a rain check. If someone weirds you out, feel no obligation to dance just because they want to. Quite often folks who weird people out just aren't that slick socially but always trust your instincts.
If you say no thanks to a dance, for example if the song is too fast, or you are tired, or you just want a break etc, then you generally sit that song out. If you say no to someone for a song for a reason other than being sketched out by them, dancing with someone else who asks you right after that is probably going to be seen as rude. If somebody asked you before or you had a rain check with someone else for that song, its ok, but otherwise it is generally bad form.
If you bump into someone else on the dance floor, it's OK, but be sure to acknowledge it. This is the time when a quick sorry is helpful. It is inevitable that folks will bump sometimes, but if you give a quick "oops, sorry" and acknowledge it, people are usually fine.
Really do try not to bump into folks. It will happen sometimes regardless. But both followers and (particularly) leaders should take care and be aware of the folks around them on the dance floor. This is called floorcraft, and it behooves you to learn it well and early.
Have fun! You may be surprised how much of a chore folks can make swing dancing sometimes. I've mentioned it a couple of times, but it bears repeating. Enjoying yourself will make-up for a lot of other shortcomings. It makes people enjoy dancing with you more, it distracts you from your insecurities, and really it is the point of the whole endeavor.
If you run up against some situation and you are feeling unsure, or you have a creepy or bad interaction with someone you can always check in with one of the Uptown Swing instructors, and we can give you our two cents. Now get out there and dance you crazy kids!
