If someone asked me out..?

I ume your going to say yes, based on what you said. Anyway, just say that you want to go out with him when he asked. Present yourself like you would if you were talking to your best friend. Don't leave right away though, he will likely be the first to leave anyway. If by chance he doesn't though and you still want to leave, make a reasonable excuse to leave. I hope that helps a little...