Walking downstairs in your pajamas – If it's just your family, and the bathroom is downstairs, it's OK first thing in the morning, as long as your PJs cover you adequately. Some people feel it's more modest to put on a robe as well, especially if you or your siblings are into your teen years.
Eating cake with your hands – If it's served on a plate, with a fork, eat it with the fork. If it's one of those little wrapped cupcakes from the store, and your hands are clean, go ahead and eat it however you want.
Eating food in a restaurant when nobody else's has arrived – This is considered quite rude. Once in a while, your food will arrive first and you'd like to eat it hot (or cold, such as ice cream). Even if the others encourage you to go ahead and eat it, it's better manners to say, "That's OK – I'll wait for everyone to be served." This also applies to family meals. Even if the serving dish got to you first, wait until your mom has been served, and lifts her fork.
Telling somebody what you intend to do on the toilet (even if close family members or friends) – Totally ill-mannered! Just quietly excuse yourself. You can say, "I'll be back in a minute or two."
