Hanging out with this girl you like while maintaining a totally carefree attitude is a sure-fire way to get her wanting your jock. If you show any signs of neediness or try to get her into you you will fail.
Just chill, have a good time and make her laugh. Let the chips fall where they may. Of course, while everything is going on watch for signs, but ignore them until she makes it super obvious that it's ok to gently make your pass.