Go with a semi-attractive girl. Then dance with her
Haha, that's what I do. Dancing is not that hard, basically all it is, is going up and down to the beat, and with today's rythm's it's not that bad. Like some of the other guys said, just move with the girl, n' that's all there is to it.
If you want to dance with a girl that you don't know, be sure she notices you first, and gives you positive eye contact.