Instructions
Open the book to the copyright page. Often, there will be wording to show the book is a first edition or first printing or show some other useful information.
See if there is a row of numbers on the copyright page. This will be an indication of the number of the printing. The number on the far right is the number of the printing. If it is a "1," it is a first edition. Collectors often only count the first printing as a true first edition. Every publisher has different rules on relaying this information. As an example, Random House does not list the "1," but it does say "first edition."
Compare the date on the copyright page with the date on the title page. If they are the same, you can assume that the book you have is a first edition.
Reflect on books printed by a small press publisher. These will generally have only one printing. If there is no mention of further printings on the copyright page, it should be a first edition.
Check over a book that you suspect is from a book club. These are not valuable to a collector, even as a first edition (90 percent of the time). They are generally condensed to make more information fit into a smaller book. The paper is often of a lower quality as well. Turn over the book and look on the back cover near the spine. A stamped image will be there, near the bottom, if it is a book club edition. The dust jacket could have "book club edition" listed on it as well. Check the copyright page for the wording as well. Also, if there is no price listed on the dust jacket, it is probably a book club edition.
Confirm your information by checking an author's signature and bibliography. You should be able to tell if what you have is the real thing by using this method.