Save the Cat deals with this a lot, too, if you need another resource. Like with most things in Save the Cat, there's a lot of wisdom in there, but also a lot of rigid beliefs that shouldn't be taken quite as orthodoxly as Snyder made it seem.

Here's a formula that I like and that seems to work really well. Someone posted this in the comments at ScriptShadow a while back:

When INCITING INCIDENT, a SPECIFIC PROTAGONIST must OBJECTIVE, or else STAKES.

A lot of the loglines on IMDb are written by fans and after the fact, they're not necessarily the loglines that were used to pitch the script or the film. Most of them just explain the basics of the story and don't really work as well as a "professional" logline should.

For example, here's the one for Moneyball:

The story of Oakland A's general manager Billy Beane's successful attempt to put together a baseball club on a budget by employing computer-generated analysis to draft his players.

That's a terrible logline, especially since it spoils the drama by saying his attempt was successful.

Using that formula here's an example:

When his daughter is kidnapped, a former spy must use his special skills to track her down before she is sold as a sex slave.

The kidnapping is the "inciting incident." It sets the story in motion.

This story is special because of the "specific protagonist" - a former spy. By putting that intriguing fact in the logline it signals what is unique about this story. His former profession ties in directly with the plot - he's not just any guy they messed with - he has special skills.

The "objective" is to find her and the "stakes" are extremely high - she will be sold as a sex slave if he fails.

Using active words like "must" and "before" gives it urgency and a ticking clock.

Try this "THE CONSTRUCTION OF A LOGLINE by Christopher Lockhart":

http://j.mp/n7wr2z

@Adaddinsane: Lockhart is a good resource, thanks.

This is not an endorsement of this contest, but if you go here, you can see a bunch of original loglines that won a Creative Screenwriting contest.