Here are two ways to express politeness. "Thank you" is widely (use) in a modern society. It is a very good manner. You should say "Thank you" others help you or say something kind to you. For example, when someone (open) the door for you, when someone says you have done your work well, when someone says you have (buy) a nice shirt, your city is very beautiful, you should say "Thank you". "Thank you" is used not only between friends, but between parents and children, brothers and sisters, husbands and wives.

"Excuse me"is another short polite usage. We use the same as "Thank you". When you hear someone say so behind you, you'd better get to know that somebody wants to walk past you without (touch) you. It is not polite to interrupt(打断)others while they are talking. If you want to have word with one of them, please say "Excuse me" first, and then begin to talk. Let's say "Thank you" and "Excuse me" the right situation.

Paula: Hi Bob. You look !
Bob: I don’t feel great, Paula.
Paula: Is there something ？Have you been to the doctor's?
Bob：No, I’m not ill. I’m just a bit tired. I’m probably not sleeping enough.
Paula: You shouldn’t go out so late then.
Bob：I’m not going out at all actually. I’m too busy . I
last night.
Paula: Staying up? But the exams are two months away.
Bob：I know, but I’ve got a lot to do. I didn’t do much last term. I wish I’d been more like you!
Paula: Well, yeah, I went to every class and I took lots of . After class I spent time looking through all the key I made during class.
Bob：Have you started preparing for the exams yet?
Paula: Not yet. I’ll probably start next week, but I’m not going to stay up all night doing it! If you don’t sleep enough, you can’t and you don’t learn anything. Anyway you should have a weekend off.
Bob：I don’t think so. I can’t the time.
Paula: Of course you can! Why don’t you go to do some work with me? You used to be a of our Helping Team.
Bob：I know, I do need some time to relax.

 you use to go to school?