Hey, that's pretty good! Charcoal is pretty difficult to use at first, and I have to say I don't usually use it for something as precise and measured as that, where simply a softer pencil will give similar results. Charcoal for me is mainly used for excessive experimentation. It's a good picture though, come to think of it, I think I attempted drawing that photo reference once. Are you using pencils to develop the picture before getting right into the charcoal work? That'll help greatly with the composition. And don't be afraid to erase anything. Draw with your eraser. Eraser + charcoal can make some really cool effects.
(is that willow, compressed or pencil charcoal, by the way?)