How do I hit the ball when it goes over my head?

If you can't reach it for a set, and you're in the back row, let it go out. If you're in the front row, make sure to call out for another player to get it. Or, you can turn around and hit it with a backwards bump. If it's the last hit on your side and you need to get it over, arch your back when you hit it. If you're just starting your attack, all you need to do is get it up so that another player can set it and then spike it over then net, hopefully getting a point. The same concept can be applied to receiving it with a backwards set.