Many writers dread writing a synopsis as they prepare to query editors and agents about their completed novel. But this vitally important bit of writing doesn’t have to be hard, and it can help the writing process as well as the marketing.

The best time to write your synopsis is before you start writing your novel and then revise it throughout the writing process. You can use the synopsis as a planning tool, and then all you have to do is polish it when it comes time to find a publisher.

The one-sentence synopsis is like the summary you find in movie listings. “An ogre, in order to regain his swamp, travels along with an annoying donkey in order to bring a princess to a scheming lord, wishing himself King” (Shrek, from the IMDB listing).

You can take a sentence like that, strip out the items specific to Shrek, and put in the same items from your book. “A HERO, in order to GOAL, PLOT ACTION along with SIDEKICK, IF ANY, in order to PLOT OBJECTIVE, in spite of ANTAGONIST.”

So it might be “A down-on-his-luck wizard, in order to get the funds to leave for a warmer island, agrees to help a mediocre wizard win the love of a princess who holds the formula for a magic potion, in the process saving the kingdom from an evil wizard who wants to use the formula to destroy the world.”

You can use a sentence like that to keep your story on track as you write it. Of course, you’ll change it along the way as you make new discoveries about your story, but that will make both the story and the sentence better. At the end, you’ll use that sentence, with small variations, in your query letter.

Just one sentence, and it will make your novel better now and more marketable down the road.