What's the 3- or 4-Act structure, and how does it relate to fiction writing?
This structure is used in plays and screenplays, but it also applies to novels.
Do you see movies? If you're a movie buff like I am, you'd have internalized the 3- or 4-act structure, which is prevalent in screenplays. I mean, I'm writing this structure without even thinking about it.
Watch your favorite movies and see how the structure works (Jurassic Park is a great one to start).
Another way to look at this is through conflict and resolution. Basically, this structure is all about rolling conflicts and resolutions, turning points, and mini-climaxes and setbacks. At the end of each act, you have resolutions and a turning point, climax, and an immediate setback. Also, there is at least one set piece at or toward the end of each act. The act itself builds up to the set piece/climax/setback, and the turning point moves the story to the following act (unless, of course, it's the final act, then it would just moves to the denouement).
Some people suggest the 25/50/25 (for 3-Act) or 25/25/25/25 (for 4-Act) division of the acts.
To me, the 1/4 structure is too rigid. Writers tend to like things in boxes. But I don't. My structure is more fluid -- for example, my second and third acts are considerably much longer than the 1st and last. But that doesn't matter -- what matters is that you have some kind of structure, instead of the plot going everywhere.
Inciting Incident vs. First Plot Point:
Your inciting incident and first plot point should happen within the first act. No exceptions.
Inciting incident and first plot point are not the same thing, though. Your inciting incident (an event that moves the story into its track) should happen rather early. In Titanic, it's when Jack and Rose meet each other -- it sets the star-crossed lovers on their tragic course (and symbolically, Titanic on its own tragic course). In the Da Vinci Code, it's when Langdon is summoned to investigate the murder. In 500 Days of Summer, it's when Tom hooks up with Summer.
The inciting incident should happen rather early in the story, if not the first page or chapter.
To me, what Hollywood calls First Plot Point (FPP) is not the same as inciting incident (II). FPP is what Campbell called "The Point of No Return." That's when things shift and the hero can't go back. In Titanic, the boat hits the iceberg, right after Jack and Rose consummated their love (which happens like 1 hour into the movie! Definitely not the inciting incident). In the DVC, it's when Langdon realizes he's being suspected for the murder and he's on the run. In 500 Days of Summer, it's when Tom realizes he's in love with Summer but she doesn't feel the same about him. In each case, the hero(es) has passed the point of no return. They can't possibly go back now.
What I expect in the set-up (Act 1) is something happening that clearly sets the stakes. In Titanic: star-crossed lovers, poor boy-rich girl, all that jazz. But the inciting incident happens early in the set up and not at the end. At the end, it's the point of no return: love vs. imminent separation by death (Rose can be saved since she's rich, and Jack will die with the rest of the steerage). But the inciting incident happens when Rose tries to jump off the boat and Jack saves her -- that sets them on the journey together, and also put Jack under Cal's radar. The iceberg is the point of no return -- love or die, literally.
Rose trying to jump off the boat, and Jack saving her: It's dramatized, and it sets them on a trajectory. It also pits Jack against Cal for the first time; he's a threat now. Also, it foreshadows the boat sinking and life/death situation later. Near the end of Act 2, Rose reminded Jack (right before the boat sinks) it was where they met the first time (at the bow). And it foreshadows how Jack is going to save Rose in more ways than she could imagine.
That's why I contend the notion that the inciting incident is the iceberg. It's absolutely not, because the story is actually a love story, instead of a boat sinking. If it's about Titanic sinking, then yeah, it's when it hits the iceberg -- that's way too late in Act 1 (which is rather long, about 1/3 of the movie). But it's about the love story of Jack and Rose, so the II is the scene at the bow when she is about to jump off.
Say what you want about Cameron as a writer (his dialogue is his weakest, I'd say), but he knows his structure. He's a master of the 3/4 Act structure. If you really want to study the structure, watch a Cameron's film.
I talked about set pieces (that there should be at least one set piece at or near the end of each act). So what are they?
Think about the scene in Jurassic Park when the T-rex first shows up and attacks. That's the mini-climactic scene... we've been waiting and waiting and waiting to see the T-rex, and it's been eluding us. Everything that came before (the car ride, the electric fence, the sabotage, outage, etc.) culminates to that. And then Mr. T shows up. That's a set piece.
Let's talk about Titanic, again. The iceberg is a set piece. It's been foreshadowed, talked about (and we know from history it will happen)... so everything before (the ship charging at full speed despite warnings, etc.) culminates to that. The boat finally sinking spectacularly is also a set piece. In a way, Rose trying to jump off the boat is also a set piece.
Basically, set pieces are pivotal scenes that change everything. The bigger the change, the bigger the set piece.
Prologue vs. Hook in Act 1:
A prologue is one way to hook the audience, especially if what follows (Act 1, the set up) is a bit tame: boy meets girl, for example. It's often done for fantasy, thrillers, etc.
But a hook can be anything, as long as it's dramatic and gets the audience's interest.
In Titanic, it's the frame story, with the treasure-hunt team and old Rose telling them the story. In Jurassic Park, it's a prologue-ish opening in which the staff is transporting the raptors and something bad happens.
In a quieter drama, for example, the hook can be more subtle but equally riveting: For example, in The King's Speech, it opens with the Duke of York having to speak in front of a grand audience, and his stammer is an utter embarrassment to everyone including himself. That's the hook, and it's not a prologue.