Ana's heard a good log line can help write a story. A log line is a one- or two-sentence description of a story that describes the seed idea. If it's focused, it can help you identify your story's best possible starting point. And it can help keep your story on track during the writing process. But what IS a log line?
Noam Kroll says: The most important components of a log line are:
The protagonist (don't use their names, just description -- for example 'An alcoholic surgeon...')
The goal of the protagonist (this is usually in line with your 2nd act turning point -- 'An alcoholic surgeon must fight for his job...')
The antagonist (and the obstacle of the antagonist -- 'An alcoholic surgeon must fight for his job after a disgruntled patient accuses him of malpractice...')
When [INCITING INCIDENT OCCURS], a [SPECIFIC PROTAGONIST] must [OBJECTIVE], or else [STAKES].
While it may be tempting to simply take the formula above and plug in the details of your story, he advises against it as it will never yield the best results. You will really want to take this one step further using the technique outlined below, which involves working backwards to find the essence of your story. This isn't a technique he created, but it is the one that by far has given him the most consistent results.
The method itself is extremely simple. You ask 4 questions about your story starting from the end and working your way to the beginning. It should also be noted that when using this formula you generally don't want to give away the third act, but rather tease the third act with points from the first and second. In other words none of your questions should pertain to anything after the 3rd act break.
When he came across this method, the example of "Back To The Future" was used, so it's referenced here verbatim. Here are the questions that were asked and their subsequent answers:
How can Marty come back from the past? (He has to reunite his parents)
Why did he have to reunite his parents? (Because he has changed the past which drove them apart)
Why did he change the past? (Because he accidently distracted his mother from noticing and falling in love with his father)
Why did he find himself in the past? (To save his skin using the invention of a crazy scientist)
Now that you have your answers you can construct a rudimentary outline of what will eventually become your log line:
"A young man, to save his skin, hides in the past thanks to the invention of a crazy scientist. He meets his future parents and accidently distracts his mother from noticing and falling in love with his father. So he is forced to bring them together or he will cease to exist."
The key is of course to make it less clunky and more focused, leaving us with something like this:
"A young man is transported to the past where he must reunite his parents before he and his future are no more."
The Who, What, When, Why and How will always force us to explain the most important parts of our story, which is why this method works so well. It's not an exact science and it's of course still up to you to decide which questions are most important to ask, but he finds that as long as you ask questions related to the turning points in your story, you'll be fine.