just like A-Dawg said, image is everything when your doing a superman .. you gotta look SICK whilst your doin it.. period. But dude, sounds like you aint getting enough momentum - you really need to run fast and dont let up when you go to dive either, cos thats gonna be your push to "glide" along the ground. To practise this I would reccomend you try running and diving faster whilst holding a pot like you would hold your marker... then try it with just your marker and bottle without the barrel then your whole marker, but progress it slowly and you'll get there fella..