Maurice Sendak's book Where the Wild Things Are is a natural intro to this project.
1. I recommend using large (15 x 22) watercolor paper as it helps the students make generous shapes that are really vivid when later painted. Drawing paper will look pale and curl up - trust me I found out the hard way! Have the students mark with a pencil the center of the paper, and then draw a circle from that which fills the top half of the paper. Explain that the students will be drawing a monster of their creation, but it must have a large head like those shown in the Sendak book.
2. Next, they should draw a body under the head. Legs and arms are to be added, along with a silly face. Lastly, details such as clothing lines and circles are drawn. Give each student a permanent black marker and ask them to trace all the pencil lines.