Although Line doesn't truly exist in nature, it's a major staple of drawing anything, let alone the figure.
In this lesson, I explain how I think of line and several techniques that have serve me and the old masters (who I stole them from) very, very well.
Hope you enjoy it.
Suggested homework:
Using the reference below, pick various body parts rather than the whole figure and try drawing that same part several times -- each time using one or two of the strategies outlined.