Get an agent if possible. Some publishers won't sign first-time authors without one. An agent will work for you to help ensure you retain as many of your rights as possible. Use the "Guide to Literary Agents" published by Writer's Digest Books or consult an online database, such as Agent Query, to find agents.
Write a brief letter to a prospective agent that tells him who you are. Let the agent know you're seeking representation for a specific work, then give a brief synopsis of the work. Follow the guidelines in the agent listing for submitting your work. Typically, you will not submit anything other than your initial letter without a request from the agent. If you have a publisher interested in your work, there's a good chance you'll attract representation for that book as well as future projects.
Don't sell your copyright. Even when your book is being published, you still own the copyright to the work. Specifically, never transfer your copyright to another party. Unless you fill out forms with the U.S. Copyright Office to physically transfer it, the copyright remains yours. Most legitimate book publishing companies don't request a copyright transfer. Besides the money you can make from your current deal, future deals could include selling movie rights, electronic rights, paperback and hardcover rights, and reprint rights. You should make money from all of these deals.
Request a clause in the contract you sign that requires further negotiations between the writer and publisher for rights other than the initial hardcover or paperback rights to your book. This clause, which is included in a typical publishing contract, can be added by the publisher and its legal team. You can review the added clause with your agent, lawyer or both.
Sell first-time rights. This ensures the publisher your work has not been published elsewhere and will not be published again within a specified period of time, and is determined between the author and the publisher. In most cases, the publisher retains publishing rights as long as the book is kept in print. Add a reversion clause to the contract that states publishing rights revert back to the author if the publisher fails to keep the book in print.
Insist on a Scholarly Publishing and Academic Resources Coalition addendum for educational or scientific material published in journals. A SPARC addendum is designed to get an author the widest simultaneous publication of scholarly work. The addendum specifies that a journal has first-time rights to publication of your article but that those rights are nonexclusive. This means you are free to publish the same article in simultaneous publications, providing you have a SPARC addendum with each publisher. This addendum also states, in the case of a book, that you are free to publish excerpts in articles separate from the primary publisher. The addendum must be added by the primary publisher at your request.