Here:
Put your feet close together (one behinf the other) then with which ever foot is farther behind push off with it and bring your other foot back. (on the the ball of your foot) Then push off with that foot. Do it on a hard wood or that weird stuff ceramic tiles or whatever they're called. It's easier, o and use some shoes with barely any grip (any old chucks will do..) You'll get better.
-edit- o yea and if you're not patient your never gonna get it. You can pull of an ok one after about a month but it'll take years to perfect.