Go for a natural smile instead of saying cheese. Though saying cheese in photos can be fun and cute (if you're a fifth grader at a birthday party), it will also give you chipmunk cheeks because your smile will be exaggerated. Instead, go for a normal, natural smile. You can even try pressing your tongue to the roof of your mouth to make your face look a bit thinner than it really is. If it doesn't feel silly, you can even do the model technique and turn a bit away from the camera before it goes off; then, turn toward the camera and smile just as your picture is taken. This will make your smile look less flat and more natural.
