We have always used a deep-dish pan gripper and a flexible, long blade cake decorating spatula. First run the spatula around the pizza to make sure it is free from the pan, then holding the pan in one hand with the pan gripper place the spatula blade along side the pizza in the pan, now flip the pizza slightly allowing the spatula blade to slip under the pizza allowing you to guide it out of the pan. Another approach is to use a cake pan with a removable bottom (just be sure to season the pan well first if its a bright metal pan). In this case all you need to do is to place the baked pizza (still in the pan) on a raised object slightly smaller in diameter than the diameter of the pan, then press down on the pan edge, it will drop away from the rest of the pizza leaving the pizza supported only on the bottom of the pan, slip a spatula blade between the pizza and the pan bottom to assist in transferring the pizza to your cutting surface. In my humble opinion, the first method is faster and more convenient but takes a little coordination while the second method is easier to master.
Tom Lehmann/The Dough Doctor