In this photo we are seeing the action during the middle of the second throw. Note the bulge of clay as the gentle force thins the walls and pushes the excess clay upward, increasing the pot's height.
To throw (or pull up as it is also known) the walls of the pot, crook your fingers and lay the side of your left forefinger at the interior base of the pot's wall. Lay the side of your right forefinger at the exterior base of the pot's wall.Your left forefinger should be slightly higher than your right forefinger, due to the thickness of the pot's floor.
Apply a slight, gentle pressure using the sides of your forefingers' joints. Begin lifting both hands in tandem, keeping the left hand slightly higher than the right. See a cut-away of the two hands' placement here.
Keep the lift vertical or move slightly inward. The clay will want to move outward; don't let it unless you mean to throw a bowl. Keep in mind that the faster the wheel is rotating, the more centrifugal force will work against you in keeping the walls vertical.
As your hands reach the upper part of the pot, reduce the pressure of your hands on the pot's wall. Otherwise, the bottom of the wall (which can resist the pressure more) will remain thicker and the upper wall will thin too much.
Once at the top, your left hand should remain stationary, supporting the clay as your right hand continues upward until it has also reached the top.
