On the Toy Story 3 extras disc, there's a segment called “Beginnings: Setting a Story in Motion,” in which the movie's screenwriter, Michael Arndt, talks about going back to earlier Pixar films (Toy Story, Finding Nemo, Incredibles) for inspiration on how to structure the first act of a movie, which he suggests should be roughly the first quarter of the movie's length.
He goes into a fair bit of detail, with examples from those earlier movies, but here's an abridged version of what he says. Bear in mind that he explicitly says this is not the only way to do things.
You [start by showing your protagonist] doing the thing they love most. Like, this is their grand passion. ... [The protagonist also] needs a flaw. ... Your character's flaw actually comes out of her grand passion.
So you establish a character; you establish the world they live in; you establish the grand passion that they're defined by; and you establish a hidden flaw that comes out of this grand passion. And then you want to establish storm clouds on the horizon. ... And then, baboom! Something comes in and totally blows apart your hero's life and turns it upside down. ... [And their grand passion] gets taken away from them.
But ... it's not enough just to ruin your character's life and take away their grand passion and change their whole sense of what the future's gonna be. You gotta add insult to injury. [Make clear that the world is unfair.]
[Now your protagonist] comes to a fork in the road, and she's gonna have to make a choice on how to deal with her new reality. There's a high road to take, a healthy responsible choice, or a low road to take, ... an unhealthy irresponsible choice. And remember, if your character chooses to do the right thing, you really don't have a story.
[The] unhealthy choice provokes a crisis. ... We're totally rooting for [the protagonist] to make the irresponsible choice.
Arndt wraps up by saying that this isn't the only way to do it, but that if you're having trouble with the beginning of your script, it's an approach to consider.
So the general idea, as I understand it, goes like this:
- Show a character.
- Show their grand passion.
- Show their flaw, which grows out of their passion.
- Take away what they're passionate about.
- Give the character a further reason to feel that the world is unfair to them.
- Give the character a choice.
- Have them choose the unhealthy-but-tempting option.
And that takes you to the end of your first act, and you can continue the story based on what happens when they make the unhealthy choice.
Half of that list would never have occurred to me. I probably won't be using this approach anytime soon, but I thought it was pretty interesting, and wanted to keep track of it for future reference, and thought some of y'all might also find it useful.