Centering of clay on the wheel is one of the most crucial parts of wheel throwing. This is the time to get the clay particles in the right place and to build on to the wedged clay process. If the clay is not centered correctly, then the pulling-up of the walls becomes a nightmare.
There are some potters who do not know that you can set the wheel to spin clockwise or anti-clockwise. Right handed potters should let the wheel spin anti-clockwise and left-handed throwers should switch the direction of the wheel head to a clockwise motion.
Throwing on the wheel is easier if you use technique instead of force. It is easier to get your arm locked on your upper leg and let you leg do the pushing and steadying instead of just your arms.
This is a video clip from the Understanding Porcelain e-course by Antoinette Badenhorst.