A synopsis is a clean, concise roadmap of the narrative arc of your story. It breaks down the characters and the chain of events in a logical and compelling way. The key word here is: clarity. Break down the most important information about your protagonist and other main characters without being too wordy. This is the time for you to explain the conflicts and how they will be resolved. Break down the emotions and motivations of your characters and how the story will evolve from chapter to chapter. Detail the main plot elements all the way from the beginning to the climax and to the resolution, including that surprise twist ending. No secrets. Reveal everything.
Less is definitely more here. This doesn’t mean it has to be dry and boring. You don’t want it to read like an instructional manual for how to set the clock on your microwave. Be energetic and use strong verbs to give a clear picture of the action and direction of your plot. Write in present tense and in third person. Try to stick to one or two pages.
And always proof your work before sending it off. It might help to have another pair of eyes scan it for any sneaky spelling errors. There’s nothing worse than having a blaring grammatical error when you’re trying to “sell” the idea of your story and yourself as a serious writer. Put the time and energy you’ve put into writing your novel into your synopsis.