Noam Kroll is an award winning Los Angeles based filmmaker, and founder of the boutique production company Creative Rebellion. He blogs about filmmaking at his website NoamKroll.com, where this post originally appeared.
The logline is truly an art form of its own. It's the one or two sentence summary of your film that not only conveys your premise, but also gives the reader emotional insight into the story as a whole. Loglines were used in the early days of Hollywood so producers could read a short explanation of a script (most often printed on the spine of the screenplay), allowing them to skip over uninteresting screenplays without even pulling them out from the shelf. While loglines today are no longer printed on the screenplays themselves, they effectively serve the exact same purpose -- to efficiently represent the story and get the potential reader interested.
While it's critical to have a good logline so that you can concisely explain your film on paper, it works just as well verbally. If you've ever tried to explain your entire feature film to someone in one sentence, you've surely found that it can be quite challenging. After all, it simply isn't possible to convey every last detail of a 110 page script in a sentence or two. And unfortunately, when dealing with anyone that can really do something for your film, all you might have is a sentence or two worth of time to get your idea across. That's okay though because you don't need to give away the entire story -- in fact you shouldn't. The goal is to sell the idea of the script, rather than the story itself, and the most effective way to do this is with a strong logline.
While the logline can serve you well both in written form and verbal form by getting the attention of producers, readers, agents, and anyone else you may want to interest -- you also need to take into account the benefit a strong logline has on yourself as a writer.
Screenwriting guru Blake Snyder has often referred to the log line as the DNA of your film, and I believe that statement to be very true. If you have a perfectly constructed logline that genuinely taps into the essence of what your film is all about, then its meaning should resonate on every page of your script. If you're ever stuck writing a scene, you can always look to that logline and it will push you in the right direction. It helps you to maintain focus on what the core of the story is really about and ultimately, your final screenplay should be a detailed extrapolation of it.