What is the rule of third? This can sound a little tricky to the uninitiated so let me delve on it a little.. Here are three simple steps on how to apply the rule.
1. Divide your entire frame into three equal parts vertically, and three equal parts horizontally. Remember where those imaginary dividing lines lie and where they meet (red dots).
2. Identify the main subject of interest in the image you are trying to capture. I call this main subject of interest as center of visual impact. This is the core of the image… the main story.
In portraiture, the main subject of interest or the center of visual impact is usually the face of the person being photographed. If the photo is taken close enough, the main
subject of interest is focused further to the eyes.
Noticed how the face of the person being photographed in the image above is being placed as close as possible to where one of the red dots are supposed to be. This is how the Rule of Thirds is being applied.
Presented below are samples of how this rule have is being observed.
Perhaps you can imagine how these images will look like if they were taken differently. The best way to understand and learn this rule is to go out and take some portraits, first by the usual way you've been taking your photos, then take more clicks by consciously observing this rule and compare your outputs afterwards. Notice how much the "story" of your photos is improved by observing this simple rule.
Happy shooting!