In drawing figures with capes a lot of people make the mistake of concentrating on the shape of the cape rather than the anatomy of the figure. Just because the body will be partially hidden by a cape doesn't mean you don't have to draw the figure anyway.
After the figure work is done then you add the cape in by creating the overall shape and form, draping it off the body parts it interacts with.
Using basic shapes to make up the body are essential in keeping the right proportions:
|Start with basic almost stick figures, then build them up.|
Keeping the anatomy accurate is important whether or not you'll see any of the figure in the final.