After all these "dance threads", I'm tired of typing long replies now.
So just some short stuff:
1) Just feeling the beat is good, but it's NOT great. Rememeber dancing is always better than not dancing, but dancing well will make you stand out.
2) Make sure you don't look "goofy". Making small moves is very average, you don't get noticed. But if you decide to do "big moves" everybody's gonna notice, make sure it looks at least good. So practice infront of a mirror. Or even better, film yourself with a camera, you will see how you REALLY look like when you dance. I don't want to scare you guys, but from experience (myself and my friends who dance a lot), you look probably much worse than you think.

But it's ok, practice makes everything perfect.
3) Just come and "grinding" up their asses shows NO VALUE on your part. So if you are good-looking, then fine, probably anything could have worked for you. Otherwise, don't be surprised if the girl goes away within 5 minutes for another guy who comes and grinds up her ass.