Composition. Any time you want to make a picture, you have to consider a couple of things. What you want to be in the picture. And more importantly what you want to leave out of the picture. Put another way, it is not just about what you place within the frame of the camera's viewfinder; just as important is what you decide to leave out of the picture.
We are surrounded by a cluttered world, take a look around and you will see. Take any scene, and however photogenic the location, there are large parts of the scene which you would just not want to include in the scene. Examples would be large electric poles jutting up into the sky, overhead wires, junk dumped outside, unwanted protrusions of any kind disrupting the scene, or just extra people and things cluttering the vicinity around your subject of interest. This we do not want to include in the scene. If we do as many point-and-shoot photographers do, just shoot what we see before us, we are likely to end up with a disappointing image. The shot fails because it lacks emphasis.
What you have to remember is this. The first rule of composition - try to simplify the scene. Your eye is unique in a way - it can scan this way and that and pick out objects of interest to look at for longer than others. The camera cannot do this ' it shows everything. Unlike a painter, you cant just leave out the distracting, unwanted, elements. What you will need to do is use the lens and the viewpoint to create an image that is as free from mess as possible. Think of the picture as a story, and use composition to make the tale as easy to understand as you can.
In most cases your pictures will become stronger if you frame the shot so that there is only one main focal point. Often, you can frame a subject so that it appears alone in the frame; however, if you include further elements, these should complement the main subject, adding to the detail of the story, rather than competing for our attention.