If you have the unpatched version of the game then this cheat will work. What you have to do is get your Speech skill up tp about 30 and go to 'Big Town' which is located north of Vault 101. Talk to the girl called Bittercup who will tell you about her dating exploits and then go to the house which is marked 'Common House' and talk to the man named Pappy. There will then be a speech skill dialogue option that says 'You came here with Bittercup, right?' and every time that you click it you get XP. Keep repeating this to get as much XP as you want.
Added by: Sanzano Oct 31st 2008, ID#3384