How should I ask her to prom?

Okay, I'm 16 and in high school. Me and this girl already pretty much know we are going to prom together, we got set up when we had just met. But, just to be official and all that, I want to actually ask her to go with me. I don't want to do something that's crazily cheesy, but any answers would be appreciated. I have a couple ideas in my head, but just want some more. Thanks!