This tip can come in useful when you're shooting moving subjects.
Occasionally you may want to have a predefined viewpoint and your subject is moving into the frame. If, like me, you normally take photos with your right eye and have your left eye closed, try keeping the left eye open so you can see the subject in your view as it moves towards the view through the camera. This makes you more prepared to fire the shutter at the precise moment.
If you use your left eye to shoot, keep you right eye open (the only downside to this is that the back of the camera, or your hand, may get in the way)