Honestly, the thing that has taught me the most about composition is PLAYING. Play your instrument, get really good at it, and learn lots of music. You'll learn so much about the way a great composition works by playing great compositions. Look at great composers like Mozart, Bach, Beethoven, Brahms, etc. They could play the heck out of their instruments. Sheesh, Beethoven barely composed at all until he was in his twenties - well after he had been established as a virtuoso pianist (and possibly virtuoso violinist, I'm not sure.) Composition lessons are great, absolutely, but playing will really help you understand the craft and the artistry. If you have an instrument teacher, ask him/her to get very in-depth with you when you learn a composition: as in-depth as they will go. I've had exactly one composition lesson in my life, but I would consider myself a much better composer than I was a year ago. Why? Because I'm a better pianist and musician than I was a year ago. I've barely composed anything between now and then, but I've still managed to improve exponentially. That's just my two cents. If you're already a virtuoso at your instrument then, well, nevermind. :D