Creating a composition for a panel is a very nice exercise and lots of fun. I usually do some doodling then try it a few more times, then do something a bit more serious, then when it looks about ok I start all the rest.
There is another approach, which is basically ripping off from a friend that has a great sense of composition but works in another area, like, let's say, photography :). Today I decided to steal another photo from a friend, in this case the photo is not that great from a technical point of view, after all it was one of the very first ones he took as a learning exercise, but the composition was there and fits very nicely with the one I had in mind. What I did is very simple and not that difficult: 1) find a nice photo, 2) either sketch it maintaining the composition or as I did with this one, actually copy the main proportions, 3) forget about the photo, concentrate on the drawing itself.
I think it works. I like the lack of perfection on proportions and the slightly skewed perspective, although I might fix some of that too. This new thing I'm doing with colors and shadows is also quite entertaining. The drawing should still get some more shades somewhere but I'll do those later.
Here is the process, in all it's glory:
The original photo is from Haripako (shusssh don't tell him). This is the second time I rip one of his photos, more to go ;).