There's one thing I don't get.
Yesterday was in a club and a girl dancing next moves closer to me and starts rubbing herself
on me. Happened several times.

From my point of view that is a clear indication of interest hence I put my hand around her waist and
start dancing with her, however then she either continues for a minute or two or just moves away like she's not interested.
Do girls do things like that for no reason or is my approaching bad?

Also when there is a group of girls dancing in a circle, and one of them starts rubbing on me like that, how do you get her to move a bit so we could look each other in the eyes? Lets say I put my hand around her waist, I always try to position myself a bit to the left or right so we could get some eye contact rather than be directly behind her. I often can't position myself like that because her friends are right next to her on both sides and I can't fit... :p

This is the great enigma of women. They do everything to be considered as a sexual object. And the moment your recognize this fact too early in anyway. You lose. Happy sarging