Ryan Leech Tutorial
http://www.youtube.com/watch?v=1du5z1fhc3w
OR
If you want to do it pedal kick style.
VIDEO BELOW:
What you do is you go on your back wheel, when you get your balance, lower the front wheel and preload, when you kick on the pedal you will go in the air, extend your body and your back wheel will go on the obstacle. If you want to go further you bend your legs in the air and then extend them back out when you get near the obstacle,that's it. - Not exactly a good tutorial, but I learn better from videos. (found this video in the video section of Trials-Forum)