Some of my fellow nerds tried to do the same thing but they made this big mistake: they'd think just because the girl danced with them, they could try for a phone number. It would make the girls really uncomfortable. Other people would see that, and it made it harder to get another girl to dance with.
I took a different strategy: I danced with any girl, made them smile (I was good at dancing with beginners and I recycled the same few jokes over and over), and then move on. Sometimes the girl would show interest and that's when I'd go for a phone number.
And if the girl wasn't interested (vast majority of the time), they'd still tell their friends how fun I am, or other people would see the whole interaction and I'd quickly feel like a rockstar.