Squiggle birds is a quick exercise that you can use to get people stretching their visual thinking muscles. It takes about five minutes and quickly, clearly demonstrates how little effort is really required to make meaningful, easy-to-read images. The main point of the demonstration is that our minds are already pattern-making machines, and very little drawing is actually required to convey an idea. The mind will fill in the rest.
I learned this exercise from my friend Chris Glynn, a fine teacher who teaches fine things.
If you like this exercise, there are a lot more on my visual thinking page.