Part of our job as photographers is to create order from chaos. This statement really does say it all with regards to creating images. When you get to a location you see everything which can appear chaotic and as an artist you must choose what you want to include in your photograph. Once you decide what you want to include in the scene you must then compose the image to make it compelling.
There are certain rules of composition that you can use to enhance your work. Actually, I hate the use of the word rule here because art should not be bound by a set of rules. That is part of what makes artistic expression cool. They really should be called guidelines but everyone else refers to them as rules so I will bend to the will of the people. You may be asking why we should be concerned with the rules and not just running around willy-nilly doing whatever we want. Visual art has been around for thousands of years and over this time these rules have been developed and studied in order to make fascinating and compelling work. You will be a better photographer for learning them. The good news is you can break them and no one will send you to jail but if you know the rules and how they function you can break them for very specific reasons to make your images more interesting.
I am going to detail perhaps the most easily employed rule and one which will change the way you see as well as your photography. The Rule of Thirds.
Rule of Thirds
Consider your camera's view finder (live view works great too). Now, imagine a tic-tac-toe grid overlaid in front of the image. Each line is in a third of the scene and each point the lines connect is what I refer to as a nexus point (there are 4). If you can place the main subject of the photograph in one of these points you will create a more compelling image. But why?
What art tells us is the eye is drawn to the center of an image because it is comfortable there. So, if you put your main subject smack dab in the middle you limit what the viewer will see and it can become boring. However, if you place the subject at one of these 4 points then the viewers eye is forced to look at more of the photograph leading their eye away from the center.
Take the image of the frog. This critter is placed in nexus point 3 with the eye very close to the intersecting lines. Your eye wants to explore all of the photograph because there is nothing dead center for it to rest on.
Now consider a landscape. The last place you want to put the horizon line is smack dab in the center of the image. For the horizon consider one of the two horizontal lines as a placement for the horizon. If the sky is what you are promoting then use the bottom if the ground is the more interesting use the top. If you also have a foreground or distant object as the primary subject try and place it within one of the nexus points mentioned.
If you learn the rule of thirds you will start seeing the world in a different way, a stronger way.