How to grind (freak dancing)?

So I understand grinding consists pretty much of the guy(me) moving in sync with the girl's hip movements.

My main question is- Assuming the girl is a complete stranger you just met on the dance floor, how long does one typically stay grinding with one particular girl? And after that period of time, how does one stop grinding with her(to go home, or to go grind with another girl, etc.)? I mean, do you just walk off without saying a word, as if nothing happened? And is it normal to talk to the girl afterwards, if she wants to exchange phone numbers, etc.?

I hope you can answer my questions accurately. If you don't want to generalize, please tell me what you would do in those situations! Please don't say, it's all up to you, etc. I'm on Yahoo Answers to get answers.. Thanks !!How to grind (freak dancing)?
If you want to ask the girl for her digits, then just ask her! If you wanna dance with another girl, then work the crowd and start dancing with the other girl. If you wanna go home, then just stop dancing and go home.How to grind (freak dancing)?
You don't do anything like that with a girl you don't know, sicko. We don't like that. Get a girlfriend.
You are asking for me not to do this, but I am going to anyway. That is the fun part about dancing and meeting ladies. You do it your way with your style. There is no set in stone way of going about it. You should probably make sure the person realizes that you are there, and that you are plunging in before just coming up from behind her and sneak attacking her. But just try to be smooth and try not to worry about it too much