It always helps to use polite words when communicating but sometimes, when learning a new language, we don’t know whether something we say is impolite or not. Here I will try to distinguish polite and informal / overly casual expressions so you will always be correct in any social situation.
1. When making polite requests, use the modals would or could (+ simple verb +) :
Would you wait a moment, please?
Could I borrow your pen?
2. Will or can (+ simple verb +) are acceptaple but a little less formal:
Will you show me how to install the new software?
Can you repeat that, please? I didn’t hear you.
3. I would like / or I’ll have. . . (not I want): I would like a hamburger and a Coca Cola, please.
4. Let me know (not tell me): Let me know when you’re available.
5. I prefer / or I’d rather / or I’m not too fond of / or I’m not a fan of . . (not I don’t like).
I’m not too fond of the mountains / I’d rather go somewhere else instead of the mountains. (not I don’t like the mountains.)
6. I disagree / I’m afraid I disagree (not you’re wrong):
It’s better to use more indirect speech when pointing our someone’s error. It’s a solfter, less offensive way to communicate your opposing view.
An even less direct way to correct someone is to say actually / or I think you’re mistaken, and then give the correct information.
We don’t want to offend anyone so keep these phrases in mind and the world will be a happier place. Also, don’t forget that please, thank you, and excuse me are universally polite and should be used often!