basically its about speed, you need enough speed to apply enough force to the tail on its rail so that it will force the board through the water. (Sort of like how a ice skater do their speed stops). You also need to throw your body into a layback position during the top part of the turn. You need to have good flexibility and strength in your legs and core to be able to stand up and ride away from a layback.
If your centre of gravity doesnt stay perpendicular to your board at all times you will fall off, especially if you havent enough speed.
Just have fun with it and it will come in time, the way i learnt was to attack the lip with as much force and speed as i could muster.