Want to know the secret to mastering digital SLR photography ? Get to know what your camera is capable of, and practice, practice, practice. The beautiful thing about digital photography is there is no time or expense involved (like developing film and prints) to see your results. You can see right away what your shot looks like. Is it under-exposed, over-exposed, out of focus? If so, change the settings, and try again. And again. And again.
Practice makes perfect, and it is true with developing your photographic style as well. You need to take lots of pictures and determine what is right for you. One great way to experiment with different settings is to try bracketing. Some digital SLR cameras have a built-in setting for automatic bracketing, but it is something easily done manually as well.
Bracketing means taking a shot, and then adjusting your settings to over-expose by one 'bracket' and again, change your settings to under-expose by one 'bracket'. If your camera has auto-bracketing, it will automatically take the three shots at once without you having to manually change any settings.
To manually bracket, decide what you want to 'bracket' – aperture or shutter speed – and take a picture at the correct exposure, and another picture stepping up, and another picture stepping down on your aperture or shutter speed. What you'll find out is that you may prefer one of the over or under exposed shot more. The lighting may look better or your subject may look more dramatic.
Mastering digital photography is probably more about mastering your camera. Learn what your different pre-set modes are (portrait, sports, night, etc). If you have aperture-priority and shutter-priority modes, try them. See what happens to your shot when you have your aperture set at f / 16 and then try taking the same shot at f / 4.5. You may like the depth of field better in one than the other. Try taking a shot of a fast running stream at a shutter speed of 1/1000 and again at 1/60. The flow of the water takes on two completely different feelings with these speeds.