Worst-case scenario: Dinner is over, and your out-of-state guests remain for more dessert and a drink. They are very relaxed. What would your reaction be? Would you (a) politely ask them to leave or (b) just walk to the door and open it?
Here are party fouls none of us should make:
Don't venture into other parts of the house without permission.
Stay away from personal rooms such as bedrooms unless invited.
Don't leave trash where it shouldn't be.
Don't eat your food, lick your plate clean, and then leave it on the table or floor. Not only is it rude, but also disgusting. Definitely clean up after yourself or simply offer to help with the dishes.
It's not your time to shine.
Don't try to stand out in the party if you're not the host. Don't leap over the couch with a drink in your hand, trip over your own feet or try a new move you just learned in dance class to get attention.
Hold it until you get home.
After all that good eating, you must be full by now. But please, do not use host's restroom to ... you know. If you can't wait, it's even more a reason for you to leave the party.
Fighting is definitely taboo.
It would be in everyone's best interest to restrain from fighting or having a heated argument (stay away from politics and religion). It's called a party, not a brawl.
Don't eat and run.
Not cleaning up after yourself is rude, but eating and running are just as bad. If you know you aren't able to stay long, don't be eager to throw back an entire meal. If offered food, say something like, "No thanks, I'm fine" or "I'll have some, but only a little. I wont be able to stay long." That way, the host won't think you just came over to avoid cooking.