Step 1: Draw something that's not a rectangle.
Step 2: Add some curves. No, really, just some basic curves. Don't get too fancy.
Step 3: Color it with a box of crayons. The brighter, the better.
What medium to use?
It's all about exaggeration, people. Exaggeration is your friend.
The more absurd, the better.
Read more about it here.