Why is composition important? It's a good portion of what will set you apart from others and make your photo stand out above the crowd. It offers the viewer a different perspective in many cases, and brings to life a subject that may just be considered mundane.
How can you help your composition? As much as I don't like this term, you need to think outside the box. Lower yourself to the ground to get perspective on blades of grass, take a corner angle on an old barn, put an old tree in the foreground. If your first instinct is to take a picture standing straight up, stop for a second and look around and you might find a different view.
In the example below, I have a photo of a storm that is a really nice image, there isn't really anything to draw the eye to.