while this isn't necessarily a tip for that actual editing of photos, it does make life a lot easier. when working with multiple different pictures, rather than minimizing and maximizing the different pictures, you can toggle through them by holding control [Ctrl], and pressing tab [Tab]. additionally, to go the opposite direction, hold shift and ctrl and press tab.
this same concept is also applied to when switching programs. just exchange ctrl for the apple key (or alt on a PC)
hopefully this is a clear description, but if it isn't just ask and i'll show you