Upon my recent post, I feared I was being far too harsh, the photographer and model are not telepathic and won't know exactly how the picture will look until it is fully developed. Yet I cannot soften my criticism any and offer that as the photographer of people as opposed to something like landscapes it is important to liberally shape the composition until it is something synonymous with the desired result. Just as it is important to know the correct aperture and shutter and every other setting a modern camera can provide us with, you are the only mirror your model has until you take the photo out of the wash and hang it up to dry. Metaphorically speaking of course. I wish you nothing but success in your future endeavors and hope that I don't sound like a cranky old man, when I'm only 18.
Continue the hard work!