1. Position your feet as you would for a nollie, and then move your rear foot slightly to the toe side of the board so that the ball is almost to the edge of the board. Don't hang your foot over the edge; this is gross-looking.
2. Pop down with your front foot the same as a normal nollie, but take your weight off your front foot right after you hit the nose to let it come off the board while it flips.
3. As you begin to rise up after the pop, flick the board with the ball of your rear foot so that it flips to the side on the way up. Don't push down - that will send the board down. And don't push too hard away from you - that will send the board way off to the side. The trick is to figure out how to flip it under you. Practice.
4. Catch this trick with both of your feet at the same time if possible. Many people catch it with their front foot first, but two feet is always more solid. This trick feels great when it smacks you hard in the feet.