When photographing anything that has eyes, people, birds, frogs or dogs, I almost always want to have my camera at the same height as their eyes. Sure, there are exceptions, but generally being at eye level makes for more compelling photos. So if you are taking photos of a child opening Christmas presents, get down on the floor. If you are shooting eagles plucking fish out of the water, be at water level. If you are taking a portrait, shoot head on with the person, although older folks do appreciate if you get a just little higher which will hide double chins and saggy necks.