Using medium force, smack the clay ball as close to the center of your wheel's bat as possible. Tuck your right elbow into the crease between your leg and torso or against the inner surface of your thigh. This keeps your wrist and hand steady; the clay can easily move just your hand. With the weight of your body acting as a brace, your wrist and hand can move the clay without having to fight.
Your wheel should be moving at full speed. Wet your clay with water or slurry. The clay should always be lubricated. If it dries out and grabs at your hands, the friction will cause the clay to go off center. Tuck the loaded sponge between your left palm and last two or three fingers. Squeeze liquid out as needed.
Using your braced right hand, push the clay inwards toward the center of the wheel head. Use your left hand to push the clay downwards. Feel free to push your clay up and down a few times. Some potters believe that this helps compact the clay even more and aids you during the throws.
The clay is centered when you can lay your finger or hand against it and the finger does not move in any way. Visually, it will look as if the clay were still, even when it is rotating at full speed.
