Have you ever read a learn to draw book? My own kiddos love them! I usually find them surrounded by a mountain of paper when they use their drawing books. In my classroom I put drawing books in the free time section for when the kids are done their art work early.
One of the kids favorites is this oldie but goodie, How to draw people and animals by Robert Pierce.
I had this one as a kid and I even drew in the back. It's a great one because it has very simple drawings and the step by step boxes are easy to follow. One day I found my daughter copying my drawing I had done as a kid.
We also use the following books: