before you try this know how to tail stall and how to kickflip really well.
1. Find a small ledge to try this on first. don't do a curb cause it's too small, but don't try this on anything over a foot and a half at first.
2. skate towards the ledge or whatever and 180 into a tail stall. it doesn't matter if it's front side or backside, but do whatever you're best at so you can be ready for the flip.
3. as you stall get your feet into a solid position. you want your back foot on the tip of the tail, and your front foot in front of the bolts (in front) with the heel hanging.
IV. do all this very fast: drop the nose about 5 inches then jump up and forward a little really high and pop the board as hard as you can. like, really really hard, otherwise you'll just fall out of the stall. anyways, as you are popping slide your front foot up a little on the blade. have the bottom of your front foot 90 degrees to the board. once you feel the tail leave the ledge or whatever, snap your front foot out really fast. the board should spin as it drops to the ground.
4. you should've jumped high enough so that you are over the board as it flips. the board may hit the ground as your feet catch it, so just make sure that your body is right above it.
4. land and skate off.
the hardest part of this is getting enough pop to do the flip. work on that by putting yourself in a tail stall position and seeing how high you can ollie out. once you can ollie like a foot high off the ledge or whatever, then try this trick. then try heelflipping out.