Alreadly answered but here's my view on them.
First off, practice. Obviously.
However practicing a trick you don't understand fully does nothing for you now does it.
Begin by putting both of your feet pointing outward (meaning, in a 90 degree angle from the bars)
| <-- Bar tube/neck/stem/whatever
- <-- Feet
Now then, come off the ramp and pull your legs upward so the back of your knees meet the back of your legs. While doing this, push your bars in the oposite direction (if you're sucking your legs up to the right, push your bars to your left). Apply more pressure down to the hand thats closest to the ground, while pulling your bars upward on the hand that's highest from the ground. This helps keep your scooter slanted completely sideways.
After meeting the mark that you wish to keep your tabletop, pull up on the hand that's lowest to the ground and push down on the hand that's highest from the ground. While doing that apply pressure to your heels to straighten out your scooter. Land, and ride away.
That's how you do a Tabletop.