Another method is the use of the grid. Albrecht Durer is well-known for using this device. In his day, it was a wooden frame with wires running through it. Today, it's easier to draw the grid right on a photographic reference.
Below is the first finished drawing from the class. The photographic reference is on the left. Using this method is a good way to learn to look for specific shapes, and to avoid drawing stereotyped symbols.Amelia Earhart (charcoal) by Arianna Crawford