Research a variety of potential publishers for your book. There are multiple writer's guides available with lists of publishers, such as "Writer's Market" or "Duotrope's Digest." Jot down any publisher that looks like a good match for your book.
Visit the websites of the publishers you chose. Look at their submission criteria and get a general feel for their website. Make a list of publishers you would like to publish your book based on how well the market fits your book and how professional the publishing company seems. Although more amateurish companies may have higher acceptance rates, you may not want your name associated with them.
Read books published by the companies on your list. In his book "On Writing," Stephen King explains, "Submitting stories without first reading the market is like playing darts in a dark room -- you might hit the target every now and then, but you don't deserve to." Although the submission guidelines on the websites will give you a general idea of what the companies are looking for, you can't get a specific idea of their needs until you actually read the books they publish.
Look for an agent. "Writer's Digest" publishes multiple guides to literary agents, and there are websites with lists of agents available online. Write query letters to agents who look like a good match for you. Introduce yourself, provide a list of credentials and ask if they would like to read your book. If multiple agents respond, send your book to only one agent at a time and explain to other agents that the book is under consideration with another agency.
Ask agents who interest you if you can see their credentials, including professional organizations to which they belong and markets to which they've sold. Agents are generally not required to disclose their client list, however, many list clients on their websites.
If offered representation by an agent, share your list of publishers with your agent and ask his opinion on your likelihood of being published in those markets. Ask him for other recommendations.
Write a proposal letter for your book. Do not say you have already finished the book, as the publisher may want input on the book's content and could fear that you will not change material you have already written. Briefly explain its premise, providing a quick summary of the book. Describe its intended audience, explaining how you know the book will sell well among that audience. Be specific about the audience without being so specific that you make it seem narrow; for instance, instead of saying that a book is for "adults who read nonfiction" or "professional Holland lop-eared rabbit breeders," you could say the book is for "anyone interested in the care and breeding of lop rabbits." Conclude by describing your credentials as an expert in the book's subject.
Create an annotated table of contents for your book. Under each chapter title, write two or three sentences about the content of each chapter. Don't include page numbers, as the book doesn't need to be finished before you submit it. Write your annotations almost like advertisements to intrigue the publisher. Rather than writing, "This chapter describes several ways to get a baby to sleep through the night," write, "The first years of parenting are an exercise in sleep deprivation, but they don't need to be. This chapter provides 15 tried-and-true techniques to get babies and their parents sleeping soundly through the night."
Write a one- to two-page overview describing your book in more detail. This is essentially an expansion of your cover letter going into more detail about what the book describes, who the intended audience is, why your book fills a niche unfilled by similar books on the market and why you are qualified to write this book.
Proofread your letter, overview and annotated bibliography to make sure they are free of grammatical errors. Give them and the first two chapters of your book to your agent to submit.
Write a three-page synopsis of your book. Include only a summary of events, not dialogue, explanations of the novel's symbols and themes or detailed descriptions of the characters' motivations.
Write a cover letter stating that you are submitting the novel and including a brief description of your previous publications. If the publishing company wants a one-paragraph description of your novel's basic premise in the cover letter, include that as well.
Proofread your letter and synopsis to make sure they are free of grammatical errors. Give them and the first two chapters of your book to your agent to submit.