I moved to the legs next, starting with the left leg. This is because it's the easier leg to add shading and detail to. Because it's not as angled as the right leg, the shadows aren't as extreme. But I still had to go back and darken the shadows on the shin because they were too light and the leg did not look as bent as it really was.

This brings up a good point about shading. The more contrast you have in your drawings, the more extreme the angles will look. In other words, if you show white as the lightest value and deep black as your darkest value, those two will create what looks like a very sharp angle. If you have a middle grey as the lightest value and deep black as the darkest value, the angle that is created will not look as extreme. To understand this in more depth, click on this drawing of a leg.