Take successive photos of your subject if there is a chance that it might move. Certain subjects, such as wild animals, won't just wait patiently for you to take your photo. In this case, take one shot quickly so that you have something to work with. Then, if the subject hasn't moved, take more shots with better positioning and composition.
As was stated in the beginning of this article, the difference between photography and good photography is a matter of education. If you know the right way to take a picture, you are more likely to get the shots you really want. Apply the advice from this article and you'll be on your way to taking the pictures you always dreamed of.
Pictures (this set already published in Russia) showing the horrors of the ww2 German/Russian campaign through the cameras of Russian soldiers.