I've learned a lot of the lessons that I now apply to my fiction, regardless of form, from reading about screenwriting.
Over at Danny Stack's blog, he's reposted some fine writing tips from Joss Whedon, originally appearing in 4Talent magazine.
Click here for Joss Whedon's top ten writing tips
My favorite quote: "Even if you're writing a Die Hard rip-off, have something to say about Die Hard rip-offs."