Keep it simple
Simple backgrounds help the viewer focus on the subject.
Having less to look at is more interesting to the viewer.
Rules of Thirds
Divide the image into thirds horizontally and vertically.
Place the horizon in the top third or lower third not in the middle.
Move either higher or lower from your vantage point
Show the viewer an angle that they don’t generally see in everyday life.
Sometimes just choosing a different lens makes all the difference.
Experiment with using different focal lengths to take the same photo.
Cropping can make or break a photo
Utilize the Rule of Thirds overlay in the crop tool in Photoshop and Lightroom to guide you in cropping.
Use of Depth of Field
A shallow depth of field will help make your subject pop out.
Use of Color Relationships
Muted color or Monochromatic
Symmetry and Patterns
Look for symmetry and patterns in texture and color.
Look for door frames, window frames, arches, bridges and fences that can frame a subject.
How does the foreground relate to the background?
I feel the most important way to get a great photograph is to pay careful attention to how the foreground relates to its background. Learn to look past your subject and see whats going on in the background as far as content, texture, color and lighting. If the background is distracting from the foreground then change camera angle, choose a different lens or vary the depth of field.