No. 1 on the list of holiday etiquette rules you need to follow shouldn't even need to be stated. Politics and turkey do not mix. Even if you think you know everyone's political persuasion, someone may surprise you. Save your political opinions for the ballot box - or your bumper sticker. Make Dinner Peaceful Again.
Half the problem with your family is that they know you too darn well, and they know your exes, too. Whatever happened to (fill in significant other's name here) and why didn't (he/she/you) ever propose? Don't engage yourself on someone's possible engagement unless they are waving a ring or a save-the-date in your face.
On a slightly different tack, if you know someone's engaged, but they're not showing any interest in unrolling the details, keep your thoughts veiled, especially if their fiance of three years is spending Christmas with his side of the family. Some engagements end in bitter breakups, not joyful ceremonies. If you're invited, you'll find out soon enough.
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Keep the fix-ups and the set-ups away from dinner. Even if your single pal wants you to make a match, don't try to pull it off in front of three generations of relatives. "How come you're not married yet, huh?" and "I work with someone whose daughter's neighbor would be just perfect for you! Do you want to meet them?" are among the rudest questions you can ask.
Kids are great, but not everyone wants to have them - or is able to do so. You might think cousin Louie would make a perfect dad, but whatever you do, don't nag him about it. To parent or not to parent is an incredibly personal decision, and any couple in your life have certainly done their own research and had those conversations in private. Oh, and never, ever assume a woman is pregnant unless you physically see the baby emerging.
The corporate ladder has plenty of rungs, and climbing them can be tricky. Even if you feel like cousin Craig should have a better job by now, mind your own business. Asking rude questions like why someone is still at that same, seemingly dead-end job, is one of the top mistakes holiday guests make.
Old family fights or scandals
Remember Doug's DUI? Cathy's complex custody battle? That fight between Greg and Gloria that ended in tears and throwing things? No. You do not. You have complete memory loss when it comes to past scandals and family feuds. Let sleeping scandals lie. Or, lie about sleeping scandals. Merely bringing one up might create a whole new one.
One old-fashioned etiquette rule we need to bring back? Don't talk about others. Few of us are exactly where the BMI chart says we should be. Some are overweight, and some are underweight. Some never check their weight, and some obsess over the scale. Unless someone is asking you for diet tips, never, ever volunteer them.
The price of anything
There's a price-conscious Pete at every event. How much did that designer purse cost? What did you pay for your house? Your brother spent how much on that new sports car? How others spend their money (or don't spend their money) is none of your business. Bringing up finances is one of those etiquette mistakes you need to stop making by age 30.
Mom said she's leaving me the diamonds, but Jan is getting a bigger share in the condo, and Aunt Ellen's getting bupkis. This is not an Agatha Christie mystery. No one is reading out anyone's last will and testament publicly over pie. If you're in anyone's will, let's hope that they will have discussed this with you privately and quietly, or you'll find out when that fatal day comes.
Complaints about the food
Holiday dinners are stressful to prepare. Most of us don't make a giant turkey or glazed ham every day, and when you're cooking unfamiliar foods, things can go wrong. If the pie's burnt on the bottom or the turkey tastes dry, fork down a polite mouthful or two and shove the rest around your plate like you did as a kid with your Brussels sprouts. There are surely enough options that no one will go hungry, and you don't need to call out the fact that Uncle Carl isn't Julia Child.
Portion size or food choices
Yes, maybe your niece should have taken more vegetables and less stuffing. Or you find it excruciatingly weird that your brother wasn't hungry for the main course, but found room for a piece of every dessert. Not your business, not your circus, not your monkeys. Commenting on others' food choices is one of the top things not to discuss during the holidays.
Unsolicited fitness tips
You know how you didn't comment on anyone's weight from that earlier tip? Neither are you going to suggest a fitness plan for them or a CrossFit center. While you're at it, refrain from telling the runner in your crowd that they are destroying their arches or bragging that you went to HIIT five times a week all of October. No one's asking, because no one cares.
We all know the stereotypes. Boomers grabbed all the cheap real estate but can't rotate a .PDF. Gen Xers are the latchkey kids of divorce who drew the short straw on everything. And millennials will be forever broke because of lattes and avocado toast. Breach that generation gap by not generalizing by age - even if some of the clichés ring true.
Very specific diet plans
Maybe you're vegan, and you swear it's given you more energy than ever. Or you think going paleo or gluten free relieved your stomach pain. Whatever trendy diet works for you might not work for everyone. If you must discuss your own eating habits and preferences, don't push it on others.
Nothing will turn a relative or friend against you quicker than unwanted parenting advice. Maybe you think Sophie is bratty, underdressed or rude for eating McDonald's rather than the holiday ham. You don't get to play Dr. Spock, especially on the one day a year you see little Dennis the Menace. Let moms and dads do their job.
You can definitely make money from your small business this holiday season - just don't pitch your products during the holiday celebration itself. Whether you're selling leggings, cosmetics or essential oils, don't view your friends and family as ready-made customers. It's uncomfortable enough when you hit them up on Facebook.
Whether or not you agree with it, pets are like children to many owners. Don't tell Grandma her poodle is too plump or you don't know how anyone can stand her beloved beagle's whiny bark. You don't have to feed, walk or clean up after their pet, and you don't get to give advice on raising it.
Bringing up religion is one of the worst etiquette mistakes you can make. Whether you're an atheist or the parish organist, you're free to worship (or not) as you choose. But a family event isn't the time or place to recruit new church members or to convince the pious that they're wasting their time.
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Clothing and jewelry choices
Maybe your holiday dinner host instituted a dress code. If not, zip it. Some people are just more comfortable in that fringed crop top or basketball shorts. If you're hosting, you can request folks dress formally or come as they are. But if you're just a guest like everyone else, playing "Project Runway" judge with someone else's outfit is only going to end in tears. Keeping your opinions to yourself and instead engaging in small talk and enjoying the people around you are the easiest ways to become the best holiday party guest ever.