The Shuv-it is one of the most fun and simple tricks in new school freestyle. It's one of the few moves that doesn't list the Vulcan as a prerequisite and tends to have a relatively gentle learning curve. On the water, I've seen several people trying it but with little success, the biggest mistake being that they try to simply jump and lay the sail over, and creating little to no lift from the sail.
Here's my take on the move:
First, find some chop. I like to find something fairly steep, not quite about to break but not so round that I don't get any natural air. Anything from ankle high to head high is fair game, but for learning knee high is best.
Once you've found your ramp it's important to line things up properly. Your board should be pointed somewhere along a beam reach in order to have enough room to carve into the wind.
Now the most important part: the carve. As hard as you can slam on your heels to carve into the wind while hanging from the boom with the sail still straight up and down. You want the board to go from beam reach to inside the no go zone as quickly as possible. Visualize yourself carving so hard that you might just do a full 360 (shaka). When done properly you'll feel the board bounce or pop off the chop.
Now it's time to lay the sail over. It's important to keep pressure on the board as if trying to continue carving in the air, if not you will most likely rotate away from the wind and kill the lift that the sail will provide. Now, at the same time you feel the board bouncing off the water extend your sail and body out across the wind. Your body should follow the sail, keeping its weight on the front arm and laying the sail parallel to the waters surface. You need to lock out your front arm and keep it straight to prevent the sail from coming back up prematurely.
At this point your sail will now create lift as wind flows evenly over both sides, so hang on and enjoy the boost.
When you're ready to land relax your front arm and the sail will flow up on it's own in a back winded position, so sheet in slightly as you touch down as not to kill all you're speed.
Summery: Carving hard and laying the sail over creates lift. It pushes the sailor higher into the air and gives the move more style and control. If you don't feel the sail creating lift, you're doing move wrong and need to do some trouble shooting to correct your form.
That's it, enjoy.