There are several ways to get XP through "devious means," here's a list of some of the most effective methods. Note: These methods are based on game bugs that may not be reproduce-able in every version of the game.

1 // You'll need to have a speech skill level of 50 or higher before attempting this trick. Approach Old Ben who sits by a fire near the King headquarters in Freeside. Persuade him to escort you to the local bar. For beating the Speech Challenge you'll get 61 XP. Follow him back to the bar and let him sit down. Speak to him again and you can do the Speech Challenge infinitely for unlimited XP.

2 // This trick requires 30 Speech skill or the Confirmed Bachelor perk and you must be friendly with NCR. Go to HELIOS One and the woman should automatically talk to you. Once she allows you access to HELIOS One, you should be able to start the "That Lucky Old Sun" mission. Proceed with the mission and talk to Fantastic and Ignacio Rivas. While talking to Rivas, make sure you get him to reveal that he is a Follower of the Apocalypse by using Speech or Confirmed Bachelor and agree with his ideals about peace or say you are neutral. Complete the mission regularly until you get to the point where you activate the Mainframe Terminal. Configure the Power Grid to "5 Full Region (Emergency Output Level)." Finish the mission by hitting the Reflector Control Panel outside on top of the tower. Go back to Ignacio Rivas, and choose the "I overloaded the plant. No one ..." option. That option will never disappear. Keep selecting that option to get 350 XP, 3 Stimpacks, and 2 Doctor's Bags.

3 // Go to Vault 11 and you will get a small quest to find out what happened there. Once you get the overseer's passcode and enter it into her computer you will be led to the "sacrifical chamber." Use a stealthboy to get past everyone and when the walls on the left open (as you walk in) go into the door and access the computer mainframe. You will be given 3 options, "Override" and "Download" for 2 conversations. Click on the second download and you get 500 XP. DO NOT EXIT THE MAINFRAME. Simply click it again... another 500 XP. You can do this repeatedly to max out your character.

4 // You will need a Barter skill of 35 or higher for this. In the southeast corner of the map you will find Cottonwood Cove (alongside the river) you will meet a man named Aurelius of Phoenix (he sometimes wanders off out of the camp). Speak to him and choose to barter with his camp for ammo...