The best way is definately to stack up something light and try to hop over it. I wouldnt suggest bricks because they fall and smash, or dont fall and grab your back wheel throwing you OTB. Instead I would use blocks of wood if you have any handy. Or if you have something that you would like to be able to hop over but think you will fall, ride up next to it and hop right beside it and get a friend to tell you if you would clear it. And as singlespeedfreeride said, dont just pull the whole bike up at once, pull your front wheel first then when it is at its peak flick your rear end up. This will make for a much higher hop and you won't look like a tool when you do it at your local skate park. One last tip, if you are trying to clear something, don't go slow at it, but don't go to fast either