A logline is a one to three sentence summary of a story, used to pitch a script to producers and other buyers.
It should contain:
- the protagonist
- the goal of the protagonist
- the antagonist
- the stakes of failure
Obviously the logline must hook the audience of prospective buyers by
- evoking a compelling mental picture
As an example, here's the logline for the movie Jaws:
A police chief, with a phobia for open water, battles a gigantic shark with an appetite for swimmers and boat captains, in spite of a greedy town council who demands that the beach stay open.
There are numerous descriptions of the purpose and structure of a logline, and many examples from real films, published in books and on websites. There are even some exercises explaining how to distill a script or novel plot into a logline, but I find they don't yield good results. Maybe my plot is not good, but maybe I don't really understand how to get from my plot to a logline, despite the vague hints in those hyped screenwriting books. So:
How do you distill a plot into a logline?
Please provide a cookbook step-by-step that even an idiot like me can follow.
Despite having provided my own "answer" below, I am still interested in this last aspect of my question: the step-by-step how-to. Most texts on the logline are very general, and don't help you much with how to make your logline hook. I'm still hoping to read your answer, so please give it a shot.