Talking Politics and Religion
This is the oldest etiquette rule in the books. Funny how the one rule our grandparents swore by is still one of the most broken today. Everyone wants to seem in-the-know. Remember, though, that there is a reason there are certain topics that are off-limits, especially when just meeting someone or sitting at the dinner table. If these touchy topics come up, diffuse the situation and change the topic as soon as you possibly can.