While working with a PSD, I often find myself zooming way in in order to make sure I can make an accurate selection with the marquee tool. Accuracy, yay!
That’s great until you’re selecting a larger area than is currently visible. Then when you click and drag your cursor to the edge of the window, Photoshop will slowly scroll the window so you can reach the other end of the element you’re measuring.
While you’re dragging your cursor though, try tapping the shift key. The PSD will suddenly scroll much faster. It can take some getting used to because the window practically jumps, but it can save a lot of time once you become accustomed to it.