Determine the genre of the manuscript. Are you writing a non-fiction book or a novel? If you're writing a novel, what sort of novel? Study books that are similar to the one you want to write. Examine the characteristics they share and how the authors developed them. Take notes and examine how the stories are created.
Read writing manuals and articles to learn how to write the type of book that interests you. Consider joining a national organization that helps writers, such as the Romance Writers of America or the Mystery Writers of America.
Notice who has published the authors you like. Visit the website for these publishing companies and read their submission guidelines. Pay special attention to any word count restrictions they have for manuscript submission. Many publishers require that manuscripts not exceed a certain length to be considered.
Write a rough draft of your book. Revise the rough draft one or two times to ensure that it is as good as you can make it. Perform one or two edit passes on your book to ensure you've caught the grammar, spelling and punctuation errors.
Join a critique group or ask two or three knowledgeable friends to read your manuscript. Ask them to go through the book and offer their input. Consider all of the suggestions carefully and incorporate those you feel improve your book.
Send a query letter to the book publishers that interest you. State the type of book you've written and that it is complete. Ask if they would be willing to look at the entire manuscript or a synopsis plus a few chapters. If you mail your query letter rather than email it, include a self-addressed, stamped envelope.
Format your manuscript for submission. Use letter-sized white paper. Set your margins at 1 inch on all sides. Use a standard font such as Courier New or Times New Roman. Include a cover sheet with your manuscript. Once a publisher has asked to see your manuscript, mail it and include a self-addressed, stamped envelope.