Let’s talk about character foils, and how to use them. We begin with a definition of character foils, expertly read by Mary. Then we talk about some archetypes, like the straight-man and the funny-guy, the hero and the sidekick, and offer some examples.
And then it’s nuts-and-bolts time: we talk about how and why to do this. Howard offers the example of Reverend Theo and Kevyn in the Schlock Mercenary books. Mary explains how she used a foil to strengthen her short story “For Want of a Nail,” (which went on to win a Hugo award.) Brandon tells us how adding a foil character was critical to The Way of Kings. Finally, Dan reveals to us (spoiler alert!) how John Cleaver and Mr. Crowley are foils for one another in I Am Not a Serial Killer.
via Writing Excuses 6.29: Character Foils » Writing Excuses.