This is one of my all-time favorite tricks to pull off, but takes time to learn how to do it correctly.
Here we go.
Place your feet on the board like you were about to do your normal ollie. But instead of popping the board like your normal ollie, you are rolling the board around your back foot in a scooping motion. A good way to get the movement down is to try it by stepping down with your front foot. The board is going to spin like a shove it but around your back foot. When you first start landing the trick your front foot might land on your nose, which is perfectly acceptable. Watch Tony Hawk and Mike Vallely show you how they land the impossible.