pretend like you are jogging or something and you twist your ankle or trip at a place that happens to be near the girl you are interested in. Mostly, if you got an audience and you can pull it off with it seeming authentic, you'll have a girl or two come over to ask if your okay or something.
*worked on me and my gf once. guy was smooth, somehow he ended up spending the whole day with us, he was so intertaing and easy to talk to, we even invited him to dinner. didn't realize we were being played until he told us that night, but it was cool.