World War II photojournalist Robert Capa once said, "If your pictures aren't good enough, you're not close enough." This is pretty good advice. If there's a lot of empty space or cluttered space or there's too much activity going on around your main subject, the viewer's eye isn't drawn to any particular aspect of your picture. Sometimes you want to show a lot of activity, but again, you don't want clutter. So move in closer and frame only the essential elements. If you can't move in closer, use a telephoto lens to move the subject closer to you. If you can't get the extraneous elements out of the frame, move yourself and the camera until you find a better shooting angle.

Capa's advice can make the difference between shooting portraits and taking snapshots.