D is for Dialogue

Dialogue is crucial in many kinds of writing. What I see sometimes in my critique partners' writing (and mine, if I'm honest) is dialogue that doesn't go anywhere. For example, "Hi, how's it going?" "Good, how's it going with you?" "Good. Thanks. So, what'cha up to?" "Oh, you know..."
Ugh. Don't do this. Dialogue needs to serve a purpose like all other writing; it should further the plot or build character or similar. Dialogue needs to sound like real people talking--but better.

As an example of good dialogue, here's an excerpt from Aaron Sorkin's Academy Award-winning script for "The Social Network":

ERICA
--I have to study.

MARK
You don't have to study. You don't have to study. Let's just talk.

ERICA
I can't.

MARK
Why?

ERICA
Because it's exhausting. Dating you is like dating a stairmaster.

It's difficult to get the full flavor of the movie (and dialogue) in just a few lines, but I think you get the idea.
For the rest of us mere mortals, how can we track down dialogue that's not working? Reading it aloud can really help.

One of my writer friends wrote a good blog entry on dialogue a while back: Make or Break Dialogue. Ooh, I see he has another: Great Dialogue. And there's one from me, too: on inconsistent dialogue. Check 'em out!

Good luck with your dialogue!