As you ollie, you drag your front foot up the board, right? Well, instead of stopping, you want to continue the drag towards the heel edge corner of your deck. Using the top of your toes, flick the board. The motion of your foot should be out, and a little down. Be careful not to just kick the skateboard down - your foot will be underneath the skateboard, making it impossible to land right. Instead, you want the motion to be both down and out back behind you.
I call the motion of your foot a "flick", because the action is quick and just with the toes. In fact, try to aim for using your little toe for the "flick". And seriously, it only takes a little strength - don't try to kick it. I know that it's called a "Kickflip", but seriously, don't kick it. You don't want any leg strength in there at all. Just a simple little flick. Like a tap. Where you flick the skateboard is just as important as the motion you use...
