The eraser marks in this hip-jutting contrapposto are left in to demonstate just how much difficulty a generic pose like this can present when drawing one from scratch.
What's on display : hips, legs
Why it works : (1) In a contrapposto, we see weight shifting from one side to the other, an alluring action in-and-of itself. (2) A good hip/waist ratio is an indicator of health and fertility. (3) There's some nice opposition between the hips and shoulders, getting us away from the redundancy of symmetry and into the exciting realm of angles.
What's important : (1) Center of gravity runs from the weight bearing foot to the sternum. (2) High left hip, high right shoulder. (3) We see some mild hyperextension in the weight bearing leg. Hyperextension is something women's limbs can do, and it should be exploited when drawing them.
How to improve : In the above shot, her visible hand appears to be pushing her hip out, so we really ought to play that up and, while we're at it, overlap her thumb. Since her left shoulder is so low, we can also safely drop her left breast slightly, placing it behind her ribcage, which is facing away from us. As a bonus, this eliminates an ugly tangent (A). Finally, since her left leg is locked and carrying most of her weight, we can freely bend her right, getting a bit more motion into it.
Rear contrapposto : Note the high, tensed buttock on the weight bearing leg and low, slack buttock on the non-weight bearing leg.
