Here's how to do it: Place your feet in the ollie position, except your back foot should be on the tip of the tail to get the best pop. Pop off your tail just like a regular pop shove it, except you give it an extra pop to make the board spin the extra 180. The hardest part of the trick is to catch the board, because it's spinning so fast. Wait until the board has turned a complete 360, land on the trucks, and ride away smoothly.
Watch experienced skaters do this trick in order to get a better understanding. After perfecting this trick, you're off to the 360 flip, or the bigspin.