Drawing SP13

I was speaking with a student at the end of class and she wanted clarification on the Form exercise I wanted you all to do. So I showed her this drawing. It has a clearly developed sense of form. And I started to wonder....once you put the lines in the right place and understand the concept- what actually makes the form POP!
1. Contrast! And I think that goes for Light/Dark as well as Line (Thick/Thin)
2. Something clearly defined and some parts blurry. Just depends on what you are looking at as to where this happens.
3. Empty space or places of calm...and then areas that are packed! Usually these also come up as you draw, one area just resolves easily and looks "formed" while others require work/reworking until they make sense!

Lastly, I was thinking about what makes a drawing appear to be finished and not just a sketch? Could you all comment here? And possibly post your form sketches and what you consider finished- and why!

Have a great break! Tom