If someone else is hosting Thanksgiving, don't do any of this stuff. Here are a few things only BAD Thanksgiving guests do:
1. Don't surprise the host with last-minute dietary requests. If you're allergic to nuts, let them know now, not the night before.
2. Don't show up empty handed, or with a surprise dish. Even if it's not a potluck, ask if there's anything you can bring. Beer and wine are things you can grab last-minute. Just don't show up with a surprise side dish...like your famous stuffing that'll put their Stove Top to shame. And don't critique their cooking either.
3. Don't expect oven space. If you're bringing something that needs to be heated up, let them know ahead of time. They might not have room, or you might not have access if they're still cooking the turkey.
4. Don't arrive early, or show up starving. It's common for Thanksgiving to start a little later than planned. So don't show up early unless you're there to help. And don't be the jerk who says, "I'm really hungry, when are we gonna eat?"
5. Don't "overserve" yourself. That includes putting too much on your plate, so other people don't get any. But also, don't overserve yourself when it comes to ALCOHOL.
6. Don't overstay your welcome. Your host will probably have to wake up early to get everything done on time. So at some point, they WILL want you to leave.