As I said before, a big part of drawing is organizing and juggling all of the elements that make up your picture into a composition that has good design and clearly communicates your idea.
Stephen Worth posted some great stuff from the Famous Artists Course on the ASIFA-Hollywood Animation Archive back in November. There's a Part One and a Part Two all about composing pictures and it really helps shine a light on the whole idea of organizing your ideas. Give it a look.
I own the Famous Artists Course but my version is (I think) a bit older than the version that Stephen is posting. Stephen's version is much better laid out and explained than the comparable sections of my course. It's really great stuff, just like everything else posted over there, so go have a look!
If you're ever looking to buy the Famous Artists Course and you're wondering which version to buy, all I can tell you is that my version came with four black binders and it appears that Stephen's is three volumes with a different color on each binder. Also be warned that here is a Famous Artist Cartoon Course, which is different. You can get either one of these series from ebay or a used book dealer, but it's sort of a gamble because you never know which version you'll get. Lastly, be aware that the Famous Artists Course is still around and they offer a contemporary course but it's really expensive and I have no idea what kind of artists are running the course these days.