In this trick tip tutorial video, professional skateboarder Colin McKay will show you how to perform a backside 50-50 on your board.
The trick to it is all in the weight transfer from your toes to your heels. When you come up the wall, just like you practiced on your neighbor's mini ramp, start with a little kick turn on your skateboard. Listen to Colin McKay, he knows his boarding.
When you're ready, go up and put the weight back on your heels until you're almost standing on the platform. That way, when you go back in, you just transfer the weight to your back foot a little bit, then lean onto your toes and lean forward to go back down the ramp's wall, just like Colin McKay.