What: The spark that breaks the balance of the hero's world and ignites their desire and journey.
Why: Without it the story stays static; the inciting incident gives the hero a reason to move and bars return.
How: Place it early, and let it change the hero's situation irreversibly, forcing a goal upon them.
Common mistake: Delaying the inciting incident too long, so the viewer tires before the story begins.
Exercise: Write an inciting incident that forces your hero into a decision they cannot take back.