Brothers Dan and Chip Heath have written a marketing book called, "Made to Stick." In it, they analyze what differentiates brands that make a lasting impression on consumers.

I'll write a review of the book another time, but it struck me how the qualities they mention (using the acronym, 'success') apply to any good writing:

Simple
Unexpected
Concrete
Credible
Emotional
Stories

When you think about it, aren't those the qualities you want your scripts, novels, short stories or articles to have? This formula might be a good one to write on an index card and keep in sight!