How to turn a flirtation into something more?

This guy and I have had this back and forth thing. I've fallen for him like stupidly and I can't get him off my mind but I'm not sure if he just thinks of it as a flirtation. I think he considers me as more than a friend, but other than that I don't know where I stand with him. We've talked about hanging out, but its never actually happened, so I wanted to hang/stand with him at our school football game this Friday (pretty much everyone goes). How should I do this without coming off desperate? Thanks :) I'm 15 btw.