Don’t show up early - Punctuality is important and arriving at the time the host tells you to is the only way to go for a holiday gathering in someone’s home. Don’t go early or you’ll probably send your host into a panic as they finish last-minute touches and showing up after everyone’s sitting down to dinner is even worse.
Tell the host about any food allergies/concerns ahead of time - Please don’t wait until Thursday to tell your host that you’re vegan or have a nut allergy. This isn’t so your host can cater the entire meal to your keto or paleo diet, but just to make them aware. And you should offer to bring something that suits your dietary needs and preferences to take some pressure off the cook.
Bring a gift - Taking something to your hostess is just good manners. Wine is always a good option, so are a wedge of fancy cheese, a bougie hand soap, or some unique coffee beans or tea.
Offer to help in the kitchen - Ask if you can do anything to help, from chopping vegetables to taking the dog for a walk so he’s not underfoot, there’s probably some way you can help your host.
Gracefully dodge political arguments, if you’re so inclined - If you’re sharing the dinner table with folks who have views you find questionable or even despise, try not to engage when someone brings up migrant caravans. A holiday dinner in someone else’s home just isn’t the time or place for that debate.