how do you do it?

To fly, go onto a hill and start running from atop the hill while pressing the 'h' key rapidly and you can turn and what not, but once you stop using the 'h' key, you'll fall.

To air dance, sit, laugh, etc, while running/hopping in the air press your Esc button twice quickly, then use your hotkeys to dance, laugh, rear, or whatever else you have your hotkeys set to, but don't manually stand up, you have to dance first! Then you can stop dancing (by pressing your dance hotkey again) and then use other hotkeys. You can't turn when your standing in the air. To get down, lay down again then manually stand up.

long description is loooooong

I hope that helped |D