"Thank you" is widely (use) in a modern society. It is a very good manner. You should say "Thank you" whenever others help you or say something kind to you. For example, when someone opens the door for you, when someone says you have done your work (good), when someone says you have bought a nice shirt, or (you) city is very beautiful, you should say "Thank you". "Thank you" is used not only between friends, but also between parents and children, brothers and sisters, husbands and (wife).
"Excuse me" is another short (politely) usage. We use it the same way 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 isn't polite to interrupt (打断) others they are talking. If you want to have a word with one of them, please say "Excuse me" (one) and then begin to talk. You should also do so when you want (cough) or make any unpleasant noise before others. Let's say "Thank you" and "Excuse me" in the right situation.
