1. If you are invited for Thanksgiving and know that the hostess usually offers to send you home with leftovers, it is OK to bring some tupperware with you and leave it in the car so that if the occasion arises, you can say, "Oh! Mary - don't use all your containers. We have some." It is not OK to bring the tupperware into the house with you. And load it up. As you fill your plate. Before you eat. You will not be invited back next year.
2. If you are invited to your friend's mom's house for Christmas, do not ask her to iron your shirts. And starch them. With light starch. "This is not Burger King," she will tell you. "You can't have it your way here."
3. Also if you are invited to your friend's mom's house for Christmas, do not tell her that you are allergic to whey. There are four other houseguests, three other children and the mom, plus there will be five other guests for Christmas supper. She is not a short-order cook. "We are from the South and eat Southern food here," she says. "Do you see whey anywhere? What is whey anyhow?" Figure out what you can eat, eat it and be quiet except to compliment and thank the cook.