Find out the name, phone number and address of a publisher who markets the type of book you wrote. Call the publisher and ask for the name of a submissions editor. Ask the publisher for submission guidelines.
Organize your thoughts. Make notes about your book's unique subject, writing style, theme, plot, or message.
Begin your letter with a paragraph or two about your book's highlights. Use a standard business letter format.
In the next paragraph, describe your experience as a writer and/or your expertise on your book's subject.
Explain who would want to read your book and why, in the following paragraph. Mention published books on a similar subject, and explain why your book is different or better.
Mention, in closing, all the items you have attached with your book proposal letter, including a SASE (self-addressed stamped envelope) for the editor's convenience.
Close your letter with a cheerful, "I hope to hear from you soon."