Learn about sword swallowing. You by reading books like "Memoirs of a Sword Swallower" by Daniel P Mannix.
Look for resources online, such as those offered by SwordSwallow.com and the Sword Swallowers Association International.
Take lessons in sword swallowing from the Coney Island Sideshow School. Check out their website listed in the resources for more information.
Practice diligently. Learn how to pass a sharp metal object down your throat into the stomach where it touches the bottom of the stomach at or near the duodenum. You must dodge vital organs to accomplish this feat. If you make a wrong move, you're either seriously injured or dead.