Shadows can be very dramatic and can add to the overall images creativity. Other times the shadow can be distracting and even non-flattering to your subject.
In the image in this post, the subject has dark hair, and as you can see the shadow is so intense that you can not see a clear outline of the models face. This particular image was take with an on-camera flash and although it was diffused, the lightsource remains quite small and was several feet away from the model. It was not intended to be a dramatic glamour shot, so there are several things that could have been done to improve this image.
These and other solutions are possible, but here we are looking at the image after it has been shot and will have to deal with it in post production. The fix is not necessary very difficult although the models dark hair makes this process just a little more tricky. Here is a photoshop technique to try:
When possible, it is better to fix the problem in camera rather than spending extensive time in photoshop in post production. When planning your shot, carefully look within the set and decide how you plan to light it. Even if you are usually natural light, strong sunlight can still cast nasty shadows. If you are shooting indoors, try a test shot with a chair or other object in the frame and make appropriate adjustments. This save you and your model time as well as make a much more pleasing image. This even applies even if you DO want dramatic shadows in your images since a little planning will get the shadows exactly where you want them!