Choose one room of your house and for one week try leaving no trace that you've used that space. The bathroom or kitchen works best for most people. If you've been doing something in that room, cooking a meal or taking a shower, clean up in such a way that you leave no signs that you've been there, except perhaps the odor of food or fragrance of soap.

Jan Chozen Bays in How to Train a Wild Elephant and Other Adventures in Mindfulness