Anyways, its not the best, but I hope it gives you the general idea. Structure lines and shapes are very helpful. They make it easier to get proportions right, and especially help with joints. Yours is very good already, and with a little practice, you'll be pro!
Let me know if you have any questions!EDIT:
I decided to add some stuff and actually explain it this time
1) A woman's shoulder's are usually about 2-2.5 times the length of her head. This means that her shoulders are approx. wide enough to fit her head, and half a head on either side. A man's shoulders are usually wider than that.
2)Young girls are generally pretty straight, but as they get older they widen out at the hips and the chest area. This creates a slight hourglass shape. How pronounced this shape is depends on the person you are drawing .
3) The length of a someone's face is different with each person. You can look up "face shapes" and find all sorts of them. It's fun to experiment with these.
4) Most often you won't need to draw ears, particularly if you mostly draw females, but I suppose it's interesting to know that your ear starts around the top to middle of your eye and ends somewhere between your nose an mouth.
