When I first came to the UK, I was having coffee with a friend. A waitress brought my coffee and asked if I wanted milk. I said: “Yes”. My friend, who was British, looked at me with a shocked expression. When the waitress left, she asked me why I was being so rude. Rude? Me? It was then that I learned that, when responding to an offer, Yes should be accompanied by please and No by thank you. As in: “Would you like some milk with your coffee?” “Yes, please”, or, “No, thank you”.
Another thing people in the UK do is saying sorry constantly. You were walking and you bumped into somebody. Say sorry. You were walking and somebody bumped into you. Say sorry! In fact, when in doubt, always say sorry. Excuse me is another useful phrase. Think of it as a tool — it can help you attract someone’s attention, whether it’s a server in a restaurant, somebody who dropped a glove, or somebody you need to pass.
Here in the US, where I`m living now, one polite thing that I always do is to thank cars for stopping and letting my cross the road as well as thank other drivers when they let me pass. Also, it’s considered good manners to say hello to the bus driver when you get on the bus and to thank him or her when you are getting off.
I also had to get used to the fact that supermarket cashiers and baggers (baggers - people who help put your groceries into a bag for you) ask you if you have any plans for the upcoming weekend or holiday. Don’t look at them suspiciously and wonder if the FBI is spying on you — just smile and briefly tell them about your plans.
Another thing that is considered a polite thing to do is to smile when you catch somebody’s eye. Let’s say you are walking down the street and you see another person walking towards you. Your eyes meet. What normally happens is that you smile and nod. Some people go so far as to say “Hi!”, or “Good morning!”. If you are somewhere like a dog park, people will often start up a conversation about your dog or the weather. That doesn’t make you friends for life — in all likelihood, you won’t learn the other person’s name and you`ll never see each other, but that doesn’t mean you can’t have a nice chat.