Unless you're skilled at tossing your pizza to get it to be the right shape, I highly recommend rolling it out on a WELL floured surface. To do this, flour your hands, your countertop, and a rolling pin. Roll it both vertically and horizontally, then flip the dough over and do the same. Flipping the dough helps it to retain its circular shape instead of shrinking back up. Continue this pattern, adding flour as necessary to prevent sticking, until you have a circular shape to fit your pizza pan.