1. Set a time frame for arrival and departure. If you start to break out in hives if anyone stays more than three days, share when it's best to come and leave.
2. Share your guest rules. Even before guests unpack or enjoy a first glass of wine, let them know any house rules, no matter how quirky, just as you would if you had paying guests through a home-sharing site. Example: Would you mind not eating except in the kitchen or dining room?
3. Voice any host expectations. Don't stew when your guest treats you like a staff member of the "Downton Abbey" household if you haven't indicated you'd like some help; not everyone was raised by Ms. Manners. If they don't offer to pitch in, sweetly say: "How about helping me chop these tomatoes for our supper?" or "I could use help setting the table." Most will get the message.
4. If you're the guest, know if a homestay works for you. If you're the type who doesn't want to spend time helping — clearing a table or stripping your bed, don't. Better to book a reservation at a nearby hotel, inn or rental. Chicago designer Tom Segal of Kaufman Segal Design prefers not to stay with friends and relatives. "I like to have my privacy, and don't want to feel I have to walk down the hall in a bathrobe, or watch TV or read with everyone when I might prefer doing so in bed," he said.