Try different f/stops ... in order to experiment with the depth of field (the range of sharpness in the scene).
Try different shutter speeds ... in order to experiment with subject motion - by freezing the action or by showing a soft blur of movement.
The act of shooting a subject, inspecting the results later (especially after the initial excitement of the shooting session has cooled down), and then returning for a re-shoot is a valuable way to develop your self-critiquing abilities ... while also improving your photographic vision.
This article is excerpted from Kerry Drager's BetterPhoto.com course: Field Techniques: Light and Composition
Article by Kerry Drager. To learn more about photography, explore the many online photography and Photoshop classes offered here at BetterPhoto.com.