The heelflip is a very difficult trick. To do the heelflip you want to make sure you know how to do an ollie and it helps if you know how to do a kickflip. Now, unlike the kickflip where you're flicking your finger off to the side towards you, you're actually going to be flicking away from you. This is going to make the board spin away from you rather than towards you. The finger positioning for the heelflip is your back finger right on the tip of the tail, so you can pop it nice and hard against the table. And your front finger right at the back of the front fore bolts. What I like to do when I do heelflips is kind of curl my front finger, just a little bit, right as I begin to pop the board. That helps me pop, and then kind of flick it away from me a lot more easily than if my finger was flat. The way I learned heelflips when I first started is try turning the board towards you, as if you're doing a front side heelflip. The reason for that is it's easier to flick the entire board away from you if it's coming towards you like this. So as you pop it towards you, you can kind of just roll your hand off the side, making it spin away from you. Once you can make the board spin away from you as it's turning towards you, then just work on, instead of turning it towards you just straighten it out a little bit more and before you know it you'll go from having heelflips like that, to heelflips that are straight. After you've mastered the heelflip you can try a few variations. You can learn to do nollie heelflips, fakie heelflips and switch heelflips. For a fakie heelflip you're moving in the opposite direction, popping off the front of the board and doing the heelflip. For a nollie heelflip you're moving in the same direction as a regular heelflip, which is forward, but popping off the nose and doing the flip with your middle finger. For a switch heelflip you're riding in the opposite direction again, popping with your pointer finger and doing the heelflip with your middle finger. And that's how you do the heelflip.