While the clay is being centered, many potters include a step called wheel wedging. Wheel wedging is mainly done to align the clay's platelets, so that throwing is easier. It also can be used to introduce a bit more water into a stiff clay or to help make certain that the clay is fully homogenized.
To wheel wedge, center the clay into a dome. Push into the middle, forcing the dome upward into a unicorn horn shape, controlling it with both hands. Once you have it nice and tall, bring it back down, controlling it so that the clay does not fold over itself, but swells from the inside outwards. Reform the centered dome.
To make sure the clay is homogeneous and to align the particles, I'd suggest at least three cycles of this.
