There are so may ways to improve the composition of a photograph. The easiest — and probably the most universal and powerful — is the rule of thirds. The rule of thirds asks that you place the subject of you photo on the “thirds lines”. Here’s how it goes
Imagine that this is your image:
As a blank slate, it would look like this:
Split your image into thirds, both horizontally and vertically:
The key is to place the subject of your image on one of those lines. Something like this:
Placing the most important part of your subject at where the lines cross is also one of the keys to getting the rule of thirds right. So, for example you can see that the feet in this image is where the lines intersect. Also looking something like this:
And there you have it! Clearly, as with everything in photography, capturing this in camera is best. But certainly this is easily achievable by cropping in post processing.