Today's quick tip is something I admit I've really only tried once. Writing purists may cringe, but if you're in the early stages of brainstorming and need to give some structure to your ideas, it might help to write up a mock trailer for your script. This way, you are forced to succinctly sum up your idea, probably with a minimum of dialogue mixed with some well-chosen visuals. You'll have to establish the hook, figure out how to introduce characters, and even give a tease of some later plot points.
If nothing else it should force you to focus on what the core of your story will be, as well as help you figure out some of the big moments.
Best of all, when someone asks you to describe your story, you'll probably be able to spit out a succinct pitch in a few sentences instead of offering one of those rambling pitches that everyone loves to hear:
"Well there's this guy... and he's in school... and his grades suck 'cuz he's spending all this time doing drugs and chasing girls. Oh, did I mention that his dad left his mom and now she's dating another guy. Anyway, he tries to get his girlfriend to give him the exam answers for the class he's taking that she's TAing, but she turns him down. They break up and he flunks out.... has to leave the campus in shame. So he goes home and finds out his mom has actually hooked up with one of his old high school classmates... it's the guy who bullied him all through high school and he's now the coach of the football team. He's home two nights but can't take it when the bully keeps picking on him, so he hits the road and tries to find his dad, who seems to have completely vanished a year ago. Oh and his estranged brother comes along for the ride... have I mentioned him yet?"
You still awake? Most of the time, you can count on the paragraph above to count for 1/5 the pitch that Mr. Hypothetical Writer will offer. While some of the stuff he mentions will probably make for entertaining viewing, the majority of it is the sort of set-up material that tends to be too much information when pitching the story. We probably only need to know that our hero was thrown out of school and that once he finds he has no place in his mother's home, he goes looking for his dad.
Homework assignment - think of 4 trailers you've seen recently and pretend you had to pitch the movie, with only the material contained in the trailer as your reference point. See if you can do it in three sentences.
Okay, that ended up being less "quick" than I intended. I also hasten to add that I in no way am endorsing this in lieu of a strong outline and a solid beat sheet. This exercise is just to get you thinking about the core of your story.