Everyone gets lazy with their photography from time to time, and when you don't pay attention to your composition, it's easy to get sloppy. I have done this in the past too. There are a lot of ways to practice and improve your composition, but here are two that I use all the time. The best part is that they take next to no effort from you.
Technique #1: Shoot Wide
One of the easiest ways to practice your composition is to shoot with a wider lens. This will ideally be 35mm or wider, but even something like a 50mm can work well for this.
The Idea behind this is that telephoto lenses oversimplify your image. When you shoot with anything over 85mm, you are really only capturing a tiny slice of your overall field of view. And when shooting subjects close to you, a telephoto lens will separate your foreground and background, making an image that doesn't have very much depth. When you choose a wide lens, your background plays a much bigger role in the image, forcing you to be creative with your background, and create balance in your image. Wide angle lenses also exaggerate leading lines, which helps to create a greater sense of depth in your images.
Technique #2: Stop Down Your Aperture
I think bokeh is one of the biggest crutches to the amateur photographer. By photographing subjects and blowing out the background, you are basically hiding any imperfections in your composition. When you stop down to something like f/8, f/16, or even something as large as f/5.6, you will show much more of your background, and good composition will become a much more important element in your photographs.
Hopefully you put these tips to good use, and hit me up if you do! I'd love to see your results.