The most often committed error is being too far away from your subject. Try to fill your frame in your viewfinder with what you are trying to show. Emphasize head and shoulder shots. You might want to frame your shot with a natural object, such as a branch from a tree arched across the top of the photo. The key to most good people pictures is how well the faces show in the final print.
Most professional photographers use flash to fill in shadows on faces, even in bright sunlight.
Look for interesting situations. Close-ups of excited children's faces watching a parade, the intimate expressions on the faces of newlyweds looking at each other, the pride in the face of a grandparent holding up their newborn grandchild, an adolescent girl showing off her first party dress, all make great people pictures. Think about your situation and compare it with how you want the final pictures to come out. Then set yourself in the right place, get ready and wait for the right expressions and take those really great people pictures.