Why
A premise is not a description of a world. It is the specific pressure that makes a particular day the first day of a story.
Most weak premises fail on one missing element. The full shape has three:
Situation — who, and what is unusual about their position. Pressure — what is forcing a change now. Clock — how long they have, stated or implied.
The clock is the part that gets left out, and it is the part that makes everything else work. A clock does not have to be literal — six weeks before the shop closes is a clock; so is a pregnancy, a season, a court date, a diagnosis. What it must do is make waiting expensive. If a character can reasonably do nothing for a month, the audience can reasonably stop watching for a month.
A premise also has to be falsifiable by the film. If the premise is "a woman struggles with her past", no scene can contradict it, which means no scene can confirm it either. If the premise is "a woman has ten days to clear her dead brother's debt", every scene either advances the ten days or does not.
The specificity is load-bearing further downstream than it looks. A vague premise produces a vague dramatic question, which produces beats with no direction, which produces scenes with no objective. It is the cheapest place in the whole production to fix a problem, and the most expensive place to leave one.
How
- Write the premise in one sentence containing a situation, a pressure, and a time limit. If any of the three is absent, it is not yet a premise.
- Name the clock explicitly, even if the film never states it. If you cannot name one, ask what happens if the protagonist does nothing — if the answer is "nothing", find a different entry point into the same material.
- Test the first scene: why today? If the honest answer is "no particular reason", the premise starts later than you think.
- Strip every adjective. A premise that needs "haunting" or "poignant" to work is describing a tone, not a situation.
- Check it is falsifiable — name a scene that would contradict it. If none could, it is a topic.
- Read it to someone and ask them what happens next. If they can guess three plausible next events, the pressure is legible.