Grinding is normal in American hip-hop clubs. It's just a part of having a good time, no need to over think it. The guys who think about how "creepy" they'll look trying to grind are the guys who are usually posted on the wall holding their drinks and staring at everyone (which seems creepy when I think about it).
It goes one of three ways:
-You grab her, she doesn't want to dance, one of you walks away.
-You grab her, she dances with you, the song ends, one of you walks away.
-You grab her, dance, escalate.
Either way, I'm having a blast in the club. There are times when there's that one bitch who wants to cause a scene (never happened to me personally, but I've seen it with bitchy white chicks blowing up at white guys who were just trying to have fun), the best thing to do in that situation is roll off of it and find a girl with better energy. Don't waste time by having a confrontation with the bitchy girl, just move on. It's pretty easy to tell who's down to dance and who's not after awhile.
Girls in groups of 3 or more are the most difficult with the grab and grind, IME. They rather dance with each other, stand in a circle and be seen, and get guys to buy them drinks. If you're with a group and your numbers are close to theirs your chances are better if your friends jump in with you, otherwise you're going to have to run game to get one of them to dance. Bachelorette parties are the easiest groups to penetrate in any case. Don't hesitate if you see them; they actually came to party.
@Cyr... As far as confidence goes: In America, just being on the dance floor is a show of confidence. The average guy is avoiding the dance floor like the plague...and forget about grabbing a girl. Not unless he's good and liquored up. Grab and grind is riskier than a normal approach because of the instant physicality, but it's also more rewarding because of the instant physicality being as sexual as it is. Besides, on the dance floor my hearing is so fucked from the loud music, I can't hear shit. Especially some chick trying to respond to me in her soft feminine voice. There's a time and place for everything; the dance floor is not the place for approaching and speaking. It is the place for grinding and making out, however.