It’s not easy to plot a story, but one simple guideline is to always ask yourself, “What’s the worst that could happen to the hero?” Then make sure that happens to the hero.
For example in “WALL-E,” the worst that could happen is that WALL-E could break down without any spare parts and that he might lose the love of his life, Eve. So what happens? The villain seriously damages WALL-E and after he gets his spare part, he loses his memory and it looks like he may lose Eve forever.
In “Die Hard,” the worst that could happen is that the villain will discover who John McClane’s wife is and that the villain will also discover that John McClane is vulnerable because he’s running around barefoot. Then that’s exactly what happens.
In “The Hunger Games,” the worst that could happen is that Katniss’s little sister will get chosen for the Hunger Games and that’s exactly what happens. Then the worst that could happen is that the other tributes will gang up on her and that’s also what happens.
Now look at a bad movie like “Cats.” What’s the worst that could happen? Maybe the hero is abandoned? Maybe the hero is forced to choose between two other characters? Notice that because “Cats” doesn’t have a clear cut worse-case scenario, the plot in “Cats” is also vague and unsatisfying. Because the worst that could happen to the hero never does seem to happen, “Cats” offers an unsatisfying story.
Another mediocre movie is “Mortal Engines,” which is about cities and towns rolling on wheels, gobbling up other towns to steal their resources. While the idea is interesting, the hero has no clear cut worse-case scenario. The hero is simply a guy in London who suddenly finds himself thrown out of the city as it rolls away. So what’s the worst that could happen to him?
Getting thrown out of the city is kind of bad, but then what? With no clearcut worse-case scenario, it’s hard to care about the hero, and that’s exactly what makes “Mortal Engines” such a weak and disappointing story.
Make it clear what’s the worse-case scenario for your hero and then make that worse-case scenario happen. That’s what makes an interesting story.