Because sports photography is quite fast paced, you'll need to start with a lot of light. If you're trying to take pictures of an indoor basketball or volleyball game, you may have problems getting good pictures. If you have a very strong flash for your camera, that will help quite a bit. Many point and shoot digital cameras don't have strong enough flash for this, especially when parents tend to try taking the pictures from the stands which are a bit too far away from all the action.
Nowadays, many photographers use photo editing software for improving the clarity and composition of sports photography shots. If you are unhappy with any of the pictures you have taken, try using such software to make the most of them. Still, an originally well shot picture has far more impact that lasts for a long time.