Gather all the bibliographical information for your book — author's name, book title, publisher and ISBN number.
Choose an out-of-print book retailer online. There are dozens of companies that have partnerships with a variety of publishers. Find the one that works with the publisher you need. Check the Resource section for a comprehensive list of companies.
Order your book. Some companies have limits to the number they can print, while others are only able to provide an electronic file. If you have access to the file you can print copies yourself, although you will be paying for the production costs.