For this trick it is important the you know how to nollie fairly high and how to backside boardslides fairly well. 

      First, you want to approach the rail with speed, the more the better. As you start to get to the top of the jump do a big nollie, the higher the better (if you get good at nollies, try to go really high, it look good). To nollie put all your weight on the nose of your board, until only your board nose of your board is touching the ground. Then jump a bit with both of your feet, and level out the board. To learn how to nollie with detail go to the Nollie trick tip. Turn your body in a F/S 90 so your facing forward. Land with the board in the middle of the rail and keep your knees bent. Stay balanced and try to keep you weight center. Keep sliding, and as your going to come off the rail, jump slightly and turn you body back or in a B/S 90 or in another F/S 90 bepending if you want to come out switch or regular. Absorb the landing with your Knees and then ride away clean! Good Luck

Pics will be up soon!