Semi Formal Dance Obligations?

I was asked as a date to a semi formal dance coming up in a few weeks. To be honest, I have no idea wtf I'm supposed to do as "the guy". It's 2 weeks before I get my license, so her dad'll be driving. Should I bring her a couple flowers or something? Or one of those pinny flower things that go on the dress or around the wrist? Help me! I don't know crap about these formalish dances.

Thanks.