****ing tango? If you're in a club that plays Hip-Hop or EDM (electro, house, trance, etc) just feel the music and express it by moving your body. It's not rocket science. Tango, salsa, and all that **** involves memorizing steps, real dancing is about losing yourself in the music. You can't teach it. Practice in your house, and go to the club every weekend and dance. You'll know you're good when girls tell you you're good. But you don't have to be a good dancer in the club. If you've ever gone into the club and just surveyed the scene, 80% of the guys dancing can't dance for ****, just get down.
As for dirty dancing, I usually get on the dance floor and dance my ass off til girls approach me. When they see you're a good dancer and that you're having the time of your life, they'll approach you.
If I do see a particularly fine ass chick who I can't resist dancing with, I try to catch some eye contact, than I start dancing up to her and get next to her. If she thinks you're cute, she'll start dancing with you front to front, than I make the move to grind. I hold her hands, turn her around, and grind my **** sore. There are no tricks to it. Just look good and show confident body language.