Rule of Thirds

The rule of thirds involves mentally dividing up your image using 2 horizontal lines and 2 vertical lines, as shown below. You then position the important elements in your scene along those lines, or at the points where they meet. 

The idea is that an off-centre composition is more pleasing to the eye and looks more natural than one where the subject is placed right in the middle of the frame. It also encourages you to make creative use of negative space, the empty areas around your subject. 

When framing a photo, imagine the scene divided up as above. Think about what elements of the photo are most important, and try to position them at or near the lines and intersections of the grid. They don't have to be perfectly lined up as long as they're close. 

You may need to move around to get the best composition. This forces you to think more carefully about the shot, and is a good habit to get into whether you're using the rule of thirds or not.

To help you out, some cameras have a setting which overlays a rule of thirds grid onto your photo. This removes all guesswork and helps you get your positioning even more accurate.

(Rule of Thirds | Photography Mad )