(Its free and worth what you paid for it.)
Practice...but practice with purpose. Pick something to refine, depth of field for example, and go shoot at various apertures with your favorite lenses and see how the sharpness changes at f/2.8 vs f.8. Figure out how to create your photographs as art, as you see them in your mind, instead of taking snaps of whatever is in front of you.
Every time I pick up my camera and head out to shoot I try to learn something new or refine a technique I already know, with varying degrees of success.
Good luck, have fun.