Composition is one of the things that many times can make the difference between a good photograph and a bad one.
Most people are taught at some point, that whatever you are taking a picture of, should be in the middle of your picture. In some cases, especially when taking a snapshot of friends and family, this centering idea is a good one. There are many other occasions though, when centering your subject, is a bad idea. Next time you pull out your trusty camera and find yourself wanting to take a picture of that pretty flower, try putting the flower in different places in your viewfinder. Then take a picture like you normally would. After you get them developed or printed, place them side by side and see which one you like the best. I'll bet it's not the one with the flower in the middle.
Below is a picture of some hay bales in Southern Oklahoma. Placing the bales just off center to the left, made for a more interesting composition than if they had been right in the middle.