Touch Her Lightly

Girls like it when a guy they're attracted to brushes against them in an accidentally-on-purpose way. A good way to brush against a girl is through a game like ultimate frisbee (you can lightly touch her back if she made a good catch or somethign to that affect) or if you're sitting together on a couch, hammock, the grass, or anything. If your hands are close enough you can brush her hand lightly and see how she reacts. If it doesn't turn out the way you want it to then you can always just move your hand onto your leg or stomach.