/ic/ - Artwork/Critique

From Tuesday's figure drawing class. I think I'm doing okay in terms of accurately judging proportion and such (at least in comparison to the rest of the class) but next week we're starting on tonal drawings, where we're not even supposed to draw an outline, and I have no idea how to do that with charcoal. Is there anything in particular I should work on in order to prepare, or should I just try to experiment with the medium using photo references?