as a guy who went to two proms, and hated both I can only give this advice. Expect TONS of drama, even from people who would under normal situations would be completely sane. It could be relationship, status, or popularity related, and it will only end badly. You will have idiots trying to spike the punch to be cool, idiots who bring their own whiskey just for themselves, and people who will wait until after to get truly smashed. Also, if your school is anything like mine, the dance floor will be more like an orgy with clothes on than actual dancing. I watched a "Grindtrain" that was literally 60 people long work its way across the dance floor like some obscene version of the limbo.
Try to ignore all that crap and have a good time. I had friends who were smart enough to avoid it and had a great time. I was stupid and let myself get caught up in it, and it ruined what SHOULD have been an awesome night. Also, the only reason anyone goes is for an excuse to have an after party. Those are usually WAY better than the actual prom, even if its just chillin with a couple of friends at someone's house.
TL;DR: ignore the stupid shit, have fun, dont let my horror stories scare you. Its more for you to be ready so you can laugh at the people who take highschool way to seriously.
Oh, and for the love of god, if someone asks you to dance, no matter who it is, take them up on it, it can only end well
