This is a lesson my grandfather taught me as a boy and I always remembered it because I thought how cool it was to be able to draw something that looked 3D.
Pictures and Video from youtube.com
Instructions:
Draw a square
Draw three equal lines at a 45 degree angle from the top corners and one bottom side corner of the square
Draw two lines connecting the three lines, one horizontal and one vertical
Draw one more vertical as shown in the corner
Add shade and shadow by considering the location of a light source
Adding shade and shadow really gives the drawing the 3D look and makes it jump off the page.
This basic lesson will help students development concepts of drawing in 3D which can be carried over into more complex drawing and art.