Shake your device to make a sim that is at their own house vomit. Then, have them clean it up to earn 6 XP in as many seconds. Note: If the sim cleaning up the puddle is at someone else's house, they will only earn 5 XP.
When you've moved a sim to another house, do not demolish the house the sim used to live in. Instead, sell the rooms by going to the build mode and pressing the 'Rooms' button, press the room you want to sell and sell it.