Good composition is like a suspension bridge - each line adds strength and takes none away.
Drawing is not following a line on the model, it is drawing your sense of the thing.
Lines are results, do not draw them for themselves.
A Curve does not exist in its full power until contrasted with a straight line.
Concentrate on a single feature - as, build all toward one eye - make all lines lead toward that eye.
Count on big lines to express your ideas.
Get the few main lines and see what lines they call out.