Here's my Rule One for body text, in an ad, brochure, or book: I don't want the reader to ever be aware of it. If the font design is noticed, even slightly, it takes away from the selling message -- or from the author's story.

How not to be noticed? Go with familiarity, with what people are used to. On the web, Arial/Helvetica is AMAZINGLY enduring, what, 60 years now? And Times Roman, though not the most readable book face because of its narrow characters, sure fades into the background for readers, particularly with some extra line-spacing (leading).

Too restrictive for graphic designers? Sure. But in business, it's about sales -- so treat your viewers with maximum readability, and restrict your design side to headlines.

And here's Rule Two -- never, NEVER, reverse out body text in an ad or brochure or web page. Light body text on a dark background is horrible. Because when you make me work at reading, sorry, I'm off to somebody else's commercial.