Find out who owns the copyright you would like to buy. This can be done through larger libraries, including the Library of Congress in Washington, DC.
Focus your effort to buy a copyright by searching for certain types of intellectual property that are considered to be part of the public domain. These may be unpublished and unregistered, providing a higher chance that you might be able to purchase the future copyright of one or more works.
Visit the U.S. Copyright Office website and search the book page for copyright information on a book (see Resources below). This is a good step to take if you are still interested in buying a copyright rather than using a work that is listed as public domain.
Take note of the database results on the book search. It will give you the author's name, the book's publisher and the claimant. Usually, the claimant is the person who holds the copyright on the book.
Write a letter to the author, and send it to the publisher. The publisher tends to serve as the intermediary for the author.
Utilize a trade organization or registry service for writers if you cannot get to the author through the publisher. One suggestion is the Author's Registry website, which has a comprehensive database of writers (see Resources below).
Hire a copyright lawyer to help you track down anyone who is interested in selling her copyright so you can buy it. While this is an expensive option, the fees involved in hiring someone reflect the amount of work and time that would need to go into such a project.