A handy rule to follow that will help you to compose a quality photo every time is the rule of thirds. In your mind, divide the image into thirds, both horizontally and vertically.
Place the most important part of your picture--the center of interest--at one of the four places where the imaginary lines cross. A person who is the subject of interest should look or appear to be moving toward the center of the picture. When taking a picture with a horizon, place the horizon line on one of the horizontal thirds, depending on the emphasis you want in the picture.
When taking photos of people, don't chop them off at the knees or ankles. Include the entire body or shoot your subject from the waist up.
Remember: Place the subject about one third of the way into the frame from the left or right and about one third of the way into the frame from the top or bottom.
