Photography Technique - Avoid Mergers
Another important consideration when taking pictures is to avoid mergers. Mergers are background elements that merge with the foreground of your picture to produce unexpected and undesirable results. A good example is a picture of a person where there is a tree in background and the tree is directly behind the subject's head. These pictures often look as if the tree is coming right out of your subject's head, this is a merger. Often, by just slightly changing your location or the angle at which you are shooting from mergers can be avoided.
Also, check out this related tip: Choose Your Background Carefully