Today I looked into a screenwriting class at PSU. They have one taught by Charles Deemer, who seems to know something about screenwriting. His advice on his website is to keep it bare and simple. Give a sketch, not a full-detail portrait.
He says that a screenplay is basically a 3-part document: set up, conflict, resolution. He writes "Once upon a time," and this is "ordinary world" - hook - which is an inciting incident and the point at which we enter "story world" - "Just when everything was going so well" - midpoint twist - "When at the last minute" - low point - "And everybody lived happily ever after, or not" (that last bit is mine).
I just saw a movie that really fits this paradigm: District 9. Once upon a time there was Wikus Van den Merwe and his happy life, then one day his father-in-law asks him to take on a big project, the extraordinary world he enters is that of the aliens, or "prawns," as the film characters call them. We have a precursor to the midpoint twist when Wikus gets the mysterious liquid on him. The real midpoint twist is when he begins to suffer the effects of the liquid.
The low point is when the powerful scientists and Wikus' father-in-law capture him and try to operate on him. He escapes from them and goes to live in District 9 with the aliens. The ticking clock is when Wikus and Christopher go to the lab to get the liquid back and work on the vehicle to get them to the mother ship. The ending isn't really everybody living happily ever after, but a sadder and wiser ending, thus making it a drama.
This is the formula I have to follow for my movie.
