When taking a picture, be aware of the rule of thirds. Split the image in your viewfinder into three parts. Place the main image into one of the thirds and have the rest of the image be background. This provides some perspective for the whole image. For instance, in this picture, I wanted to focus on the eyes, so they took up the middle third of the image. The space provided by the other two-thirds allowed my viewer space and time to focus in on the eyes.
However, in the picture below, I wanted the viewer to see my daughter in relationship to where she was and what she was doing. So I put her whole body into only one third of the picture and let the other two-thirds tell the story of what she was doing.