What are the best settings for a dslr for shooting action shots?

If you use shutter priority (TV), you may inadvertently underexpose your images, if there is insufficient light- as there almost always is in most gyms. I like aperture priority with a higher ISO (800 or above), if you aren't using any flash. With a fast, 2.8 lens, and the aperture set wide open, the camera will select the fastest shutter speed possible. If it's faster than 250th of a second and you want greater depth of field, or less digital noise, either select a slightly smaller aperture or a lower ISO.