Most literary agents and publishers require an author to submit a 3-5 page synopsis. Some want a longer synopsis, while others want a one-pager or a detailed chapter-by-chapter outline. My advice is to create a 3-page synopsis since that will suffice most requests and customize it as needed, but always keep the original 3-pager as a template.
Format
The format should be much like the manuscript itself, double-spaced, one-inch margins, a header with page numbers, and a font in Times Roman Numeral or Courrier. The entire synopsis must be written in present tense and it is best to use third person POV even if your story is written in first person.
As writers, it is drilled into our psychological mental space to write in a way where we show, don’t tell. The synopsis is where you throw that concept out the mental window and write everything in a telling format. There is no other way to condense hundreds of pages down to a few pages without this skill. Stick to the main highlights of the story and the critical turning points.
Introduction
The first lines should contain a hook, introducing who the hero is and what he wants, and who the heroine is and what she wants. Then the next few lines should explain why they can’t have what they want, making the external conflict immediately clear. You don’t need to include a lot of backstory, only enough to get the main concept across to an agent or editor.
Setting
Give a brief overview of the setting, which would include time period, location, and culture. You don’t need to get into specific details, but flavor the synopsis with enough sensory to make the editor imagine the story and feel the setting. This is not a time to showcase your character dialogue skills, or deep POV sensory descriptions.
Characters
Concentrate on the two main characters’ personalities and reveal their inner conflict. I usually alternate paragraphs that indicate each character’s point of view. Try to only mention the hero and heroine, however, if you must mention a third or fourth character whose influence is essential to understanding the story, try to only mention them by their profession (doctor, lawyer), or relationship (mother, sister, brother). Introducing too many characters in so few pages can be overwhelming and increases the chance of confusion, a perfect reason to reject your proposal without requesting the full manuscript.
Genre
Show the development of the plot regarding the genre you’re writing, whether it be romance, suspense, mystery, fantasy, inspirational, etc. If it’s a romance, this is where you tell about the characters’ physical attraction, how they fight the attraction for whatever reason, and how they eventually break down to acknowledge the attraction. Then discuss the progression of the relationship to the caring phase and the love phase.
Faith
In an Inspirational romance or Christian fiction, make sure you indicate what kind of spiritual state both characters are in at the beginning of the story. Are they believers? If they are, what are their spiritual flaws? What are their weaknesses? Talk about new realizations and discoveries that begin to change their mind. End on how they’ve changed as a result. Either the characters must find salvation, or if they were already believers, then they must have grown in a spiritual area. Think about the different fruits of the Spirit for areas to improve your characters.
Climax
Just like in your story, build the synopsis to the climatic point. Bring the inner and external conflict to a head, relate the spiritual tension, and make the situation look impossible to resolve.
Resolution
Tell how the characters resolve their conflict and what plot changes occurred to enable them to achieve their goals or remove the problem. Be sure to include how the story ends. Editors and agents won’t appreciate being teased. They want to know that you can bring the book to a satisfying end before they’ll be willing to invest more time in reading it, or before they will consider advocating it to their team in consideration of buying it.