Find a publisher that might be interested in publishing your type of book (see Resources below). There are many publishers out there that specialize in certain fields, so make sure you pick a few that will be interested in the type of book you've written.
Find out what the submission guidelines are. These submission guidelines often set a word length limit, topic guideline and instructions for sending a manuscript. Usually, publishers will want a query letter and a synopsis, and this information will be listed along with the publisher's contact information.
Write a query letter. In this letter you will pitch the book idea. Explain what you sought to accomplish in your book and why you think your book will be worthwhile to publish (see Resources below).
Write a synopsis. Tell the editor everything about the book. Tell the editor both the content of the book and why you made the decisions you did when writing the book.
Send the entire package to the publisher(s), along with a self addressed stamped envelope (SASE).
Wait for a response. If your idea is rejected, revise your query letter and synopsis, find another publishing company and repeat Steps 1 to 5 .
If an editor replies and asks you to revise your work, do so according to his suggestions. If your manuscript is accepted, you will receive a letter with further instructions.
Write for smaller publishing markets before trying to find a literary agent.
Find an agent that specializes in your niche. These agents can be found in annual guides which can be purchased at a bookstore or online. There is also a database of literary agents in the Resources section below.
Follow the same steps as in Section 1 above.
Take feedback, ignore rejection and be prepared to submit to many agents.