I give a base diagram for the rule of thirds below, but essentially this fundamental element of design plays on the visual aspect of the photograph. As a viewer looks at a photo, the natural tendency for the eye is to look at certain points of the image first. Asking anyone on the street, they would probably tell you that the first place to look is at the center, but they would be wrong.
Using the rule of thirds, you would basically split the horizontal and vertical portions of the frame into thirds, as shown above. There are four (4) points on the diagram that intersect (vertical and horizontal lines cross); the upper left, the upper right, the lower left, and the lower right. These are the points that a viewer's eye naturally is drawn to when first looking at a photograph. These are the main points to concentrate on, but typically anywhere along the lines either vertically or horizontally that the primary focus of your photograph should be placed. There are exceptions to this rule, but let's stick to the basics for now. If you are taking a portrait of someone, you would want to place him/her along the dividing lines of the frame. This will create a more visual pleasing photo to look at.
As I have said before, this is probably one of the most fundamental rules of photography. With that being said, it is also the most unused element of design. I would recommend a training program of sorts for the amateur photographers out there. Go out and take a lot of photographs, it doesn't matter what it is, just take them. First concentrate on what is your primary subject of focus and then apply the rule of thirds. This fundamental can only be instilled if it is practice, much like driving a car, the more you drove a vehicle the more comfortable and confident you drove. The same is for applying this rule. Practice, practice, practice. I cannot say this enough.
