Upon signing up, players choose rules to follow for the duration of the month. Choose from suggestions like, "limit caffeine," "drink enough water," and "limit soda." You're then prompted for more detail. For example, after choosing "drink enough water," you're prompted to disclose how much you drink, how much you want to drink in the upcoming month, how difficult you think it's going to be, and how important the rule is to your overall goal. Following your rules nets you "life points," breaking them takes points away.
Find out more about the game after the break.