In most portrait photos, the subject's eyes look directly into the camera. Have your subject express a variety of emotions to capture a unique photograph. You could also try to have the people in the picture look at something in the frame.
A great photography tip is to bring your camera with you wherever you go. You never know when an awesome opportunity might present itself. If you don't have your camera during these moments you'll definitely regret it later. Always try to bring your camera wherever you go.