Here are some polite expressions commonly in use:
You say excuse me when you want to go past somebody.
You also say excuse me to somebody you do not know when you want to attract their attention.
I beg your pardon is a formal expression when you need to apologize for something.
ex. I beg your pardon! I must have picked up your bag by mistake.
sorry or I'm sorry is used frequently. So also Pardon me and excuse me are used for apologies.
You use the phraser I'm afraid... when you want to apologize because you have to tell somebody something that they may not like.
ex. -'Has the last bus gone?' - 'I`m afraind so'
I`m afraid there's been an accident.
You use expression which show hesitancy when you are asking for a favor: Modal verbs could & would are used for polite expressions.
Could you just help me move these boxes, please?
I wonder if I could have a copy of your article?
Would you mind if I leave a few minutes early today?
Would you mind letting me leave the class at 12?
Do you think I could borrow your car this weekend?
You say please when you ask for something.
Please could I have the menu?
Could I have the menu please?
When you want give direction to some one; say:
Please come back later.
Wait a moment please?
Can I have that today, please?
when somebody gives you something, or when you buy something or recieve information, you are expected to say Thank you or Thanks.
It is not usual to say anything in response to Thank you in British English, although some people may say That's all right, That's okay or Don't mention it.
in American English You're welcome is common.
cheers is often used in informal British English to mean Thank you.
ex. : -'here's that 10 Euroes I owe you' - ' oh, cheers'