INSTANTLY FIND THE CENTER OF ANY OBJECT

This is a great tip for quickly finding the exact center of any object on its own layer. You start by pressing Command-T (PC: Control-T) to bring up the Free Transform bounding box. The bounding box has a handle in the center of both sides and center handles at both the top and bottom. Now all you have to do is make Photoshop's rulers visible (Command-R on Mac, Control-R on PC), and then drag out a horizontal and a vertical ruler guide to these handles to mark the center.