Seek the services of literary agents. Book/literary agents find a publisher by matching your manuscript to the publisher; they help you develop your manuscript and may also negotiate a contract for you. Create a submission package that matches the agent's preferences and send it to them. Keep close contact with the agent to ensure that they are working on your book. Guide to Literary Agents and the Writer's Market are useful resources for finding an agent.
Join or create a writer's group. These are local groups of writers who come together to offer support, assistance and literal critique among themselves. They offer connections and an extensive network into the publishing world. Choose a group that meets your needs as a writer and business person, while also encouraging you to grow as a person. Choose a group that has keen interests in commercial publishing.
Use the Writer's Market site to find reputable publishers who are accepting manuscripts. Through this site you are able to manage your submissions, stay abreast with the latest publishing industry news and also gain advanced publishing and marketing knowledge. Once you are able to make contact with a publisher, you will be furnished with all the information on how to go about publishing your book.
Take into consideration the legal requirements that go into publishing a book. An understanding of Copyright issues as well as contract law will help you in getting the most out of the agreement between you and the publisher.