Its not really that hard, you just start with the staff over your head spinning one way then you turn the opposite direction to the direction the staff is spinning and pass the staff behind your back, then you sit down whilst still turning the opposite way to the staffs spin, and then sit up.
Basically you take two 360 degree turns, one with the staff behind your back and one with it over your head whilst you are sitting and turning.
It looks better the faster you do it and the more energy you put into springing back up, very cool adn also a recovery if you ever fall over whilst doing a behind the back spin
(I wonder if thats how Xaeda figured it out????? lol)