One easy to remember photography tip that will improve your shooting is to have the subject "looking" or "moving" into the frame. This means the subject should be at one edge of the frame appearing to look into or go into the empty space in the shot, rather than staring at the edge of the frame. A subject that looks into the frame or motion that leads into the frame gives the viewer's eyes some place to go.
FOR SUBJECTS IN PROFILE
In the above photographs of a great blue heron and of beloved puppy Kiki, both subjects are shown in profile and both are looking into the empty frame. If I had composed the shots with the empty space to the right, the images would look awkward and unbalanced. When photography a subject in profile, be sure to include enough space for that subject, and the viewer, to look into.
FOR SUBJECTS IN MOTION
Likewise for subjects in motion, they should also have plenty of space to "move" into in the frame. This allows the viewer to look and see where the airplane is flying. The Jeep below suggests a continued movement and leading action. Having empty space to either the rear of the plane or Jeep would not only look awkward but show that we were too slow on the shutter to catch the action.
FOR SUBJECTS LOOKING INDIRECTLY
When a subject is looking indirectly in the frame, space should still be given in the composition in the general direction the subject is looking. The flamenco dancer above is facing the lens, but looking to her right. Composing for more space on the left of the frame makes the viewer also look left. The wedding couple below are really looking indirectly in the frame, but overall both their poses and the directions of their eyes favor viewing from top right toward bottom left.
Keep the "look into the frame" composition tip in mind to produce photographs that give the subject and the viewer space to look into and avoid subjects staring into the edges of the frame.