RULE OF THIRD

The rule of thirds is a powerful compositional technique for making photos more interesting and dynamic. It's also perhaps one of the most well known. Using the 'Rule of Thirds' is not something that you have to do, but it goes a long way to improving your photography.
The rule of thirds states than an image is most pleasing when its subjects or regions are composed along imaginary lines which divide the image into thirds — both vertically and horizontally:

The rule of thirds is applied by aligning a subject with the guide lines and their intersection points, placing the horizon on the top or bottom line, or allowing linear features in the image to 
flow from section to section.

How to apply rule of third

1- Check your camera to be sure it has a grid

2- With this grid in mind the ‘rule of thirds’ now identifies four important parts of the image that you should consider placing points of interest in as you frame your image.

The theory is that if you place points of interest in the intersections or along the lines that your photo becomes more balanced and will enable a viewer of the image to interact with it more naturally. Studies have shown that when viewing images that people’s eyes usually go to one of the intersection points most naturally rather than the center of the shot – using the rule of thirds works with this natural way of viewing an image rather than working against it.

3- With the 'visual' of the rule of thirds, take a photograph. Be sure the subject of your image is at the crosshatch whenever possible. Even if it isn't at the crosshatch, but at the location of a third; left, right, top, bottom. In this screenshot, you see that the eyes are at the top third.