You could be rude, even when you think you’re being polite! Here are the facts, courtesy of etiquette expert, Peggy Post.
First, you may think it’s rude to admit you can’t remember someone’s name, but that’s false. You might be able to avoid admitting you’ve forgotten their name if you run into them once when you’re alone, but see them regularly, especially if you’re with other people, skipping the introductions is rude to everyone involved. Your best bet: Say something like, “Forgive me, I remember meeting you at that party, but I can’t recall your name, I’m John.”
Another etiquette mistake: RSVPing only if you’re actually going to the event. The truth is, you should respond to every invitation, even if you send a text or an email that says, “I’m so sorry, I can’t. Let’s get together another time.”
Then there’s asking your host for a tour of the house. Post says that’s only appropriate if it’s a housewarming party, because that’s the only time you know the whole place is spic-and-span. At any other time, they might’ve run short on time, and tossed a pile of junk in the back bedroom, and they’ll be embarrassed for you to see it. Plus, you shouldn’t take the party host away from their other guests to give you a tour.
And the last etiquette mistake: You’re invited to someone’s home for dinner, and you explain that you’re on a low-carb diet. Post says that guests have no more business telling their hosts what to cook than they do telling them what to wear. The only exceptions: Religious restrictions, and serious food allergies, which means, it's okay to say, “I'd love to come to your clam bake, but you should know that I'm severely allergic to shellfish.”