Complete your manuscript. Only established authors can sell a book based on an idea or outline. New authors must have a finished work in order to submit and sell it. Having sold only short stories does not make you established to sell a novel based on an idea.
Print your manuscript according to proper manuscript formatting. Use a serif font (Courier is still preferred) and double space the lines. Set a 1-inch margin around the sides, top and bottom. Place a header on every page with your name, the title and the page number. On the first page, in the upper left corner, type your full contact information. Do not use fancy fonts or types, and don't use bold. Instead of using italicized words, underline the word to indicate you want italics. Make sure your manuscript is free of spelling or grammatical errors.
Select a publishing house that publishes books like your manuscript. The house should also accept unsolicited manuscripts from writers without agents. This will be stated in their guidelines, which you can usually find on their website. If not, phone the publishing house and ask them to mail you a copy of the guidelines.
Prepare your manuscript using Steps 1 and 2 in Section 1. Individual agents may have specific formats, but most will expect the same formatting used by publishing houses.
Write a query with a letter describing your project and send it to as many agents as you can. The agent listings will tell you if they also want a sample of the writing and what they will want (for instance, the first chapter). Send the query letter through the postal mail, which is more effective than e-mail.
Mail the manuscript in a box or bubble envelope. For the returned manuscript, have it inside a smaller box or corrugated cardboard envelope that fits inside the mailer box. Also include a SASE envelope in the event the publisher wants to keep your manuscript and needs only send you a letter regarding its publication. Include in your package a cover letter with a paragraph about your manuscript and any relevant, personal information that would either confirm your expertise in the area or establish your publishing credits.