Find an open area with about 30 yards of running space. Choose and starting point as well as an end point. From the starting point, sprint as fast as you can to the end point. Once you've reached the end point, walk back to the starting point. As soon as you've reached the starting point, sprint as fast as you can toward the end point. Continue repeating this until you've done 15-20 sprints. Add more sprints as you progress.