Instructions
Travel to Vault 11, which is located to the west of Boulder City. Enter the vault to begin a quest to gather information about the purpose of this vault.
Interact with the computer terminals that you find as you explore the abandoned vault to gain information. Play through until you learn the Overseer's password.
Enter the password into the computer in the Overseer's office. This will open a tunnel hidden under the desk that leads to a sacrificial chamber.
Head down the tunnel, and enter the chamber at the end. Sit down in the chair in the room to begin a slide show that attempts to convince the sacrifice that they would be rewarded in the next life. After the slide show, the walls on both sides of the room will open to reveal turrets and armed robots that will seek to kill you.
Kill the robots and turrets to preserve your life. If you have a Stealth Boy, activate it to become invisible and simply walk past the aggressive robots.
Enter the small room in the back of the chamber to find the vault's mainframe. Access the mainframe, and select the third dialog option on the list. Selecting this option will grant you 500 experience points and return you to the main three dialog options. The glitch maintains the third option rather than removing it from the list after you've selected it.
Continue selecting the third dialog option to gain as many experience points as you like. When you're bored and you want to move on, unlock the door to the chamber using the other dialog options, and head back up through the tunnel.