Fail to do your chores, and the house falls apart -- soon, you're living in a smelly, cluttered wreck of a place, and the landlord is banging on the door with an eviction notice.
But lacking a system, chores tend to fall into a nasty cycle -- one roommate, the most responsible, hassles and berates the other roommates, who tend to blow chores off for as long as possible. The responsible roommate resents all his or her lazy roommates, and the lazy roommates get passive aggressive about the constant complaining and actually blow off even more work. It's a fist fight waiting to happen.
Thus, before everyone has even moved in, it's a good idea to meet up and set some clear rules.
The more explicit your household list of chores is, the better. If that means you have colorful magnets on a grid hanging from the refrigerator, so be it -- actually knowing what day what person is responsible for what chore is absolutely key to getting that chore executed. Even people who aren't naturally lazy or downright unhelpful will tend to skip work that they're not sure they need to be doing... so make it clear who needs to be doing what.
Oftentimes, the punishment for not doing chores is that someone else does your chores and then glares at you later. This is not an effective punishment.
A much more effective way to punish failure to do chores is to make the shirker do the same chore the next week... along with whatever other chore he should have been rotating into. Or if a roommate blows off dish night, guess what -- it's still dish night for her the next night and there just happen to be more dishes! Talk this out ahead of time as a group, so everyone understands -- failure to do work means more work.
It's not a bad idea to create an "enforcer" position in the house -- someone who, possibly for a slight rent break ($10 or $15 a month), is tasked with making sure the chore schedule is both up to date and followed. Nagging people to do their chores and making sure all chores are spoken for is not an easy job, but even a tiny bit of financial recognition can go a long way to making it something a roommate will pursue with passion.
If chores are a chronic problem and there's just no getting around that, have everyone in the house pony up a medium-sized pile of money -- something in the $100 to $200 range. That money can sit in an account or envelope, to be returned at the end of the year.
The catch? If you blow off a chore, someone else can do that chore and take a set amount of money from your deposit. Perhaps the trash is $5, vacuuming and surfaces $10 -- set your own numbers, and make it clear that if you fail to perform at your household chores, there's a consequence -- and a reward for the roommate who steps up.