But if someone asks you, and you say: 'Oh no, I have a wife, ' you're done, it's clear, you can do whatever you want.

CNN: In the Field

This means that if someone asks for leftovers, you say, "I'm so glad that you enjoyed the meal, " and wrap up a wedge of quiche.

CNN: Navigating family and dinner table etiquette landmines

For example, if someone from "IT support" calls you and asks for your password so they can help fix your problem, how do you know they haven't called everyone else in the building first until they found you who has really got a problem?

BBC: Viewpoint: How hackers exploit 'the seven deadly sins'