The words we can use are;
Formal ways
- Good morning!
- Good afternoon!
- Good evening!
- Good night!
- How do you do?
- How are you?

Informal ways
- Hallo
- Hi
- How are you keeping?
- How’s life?
- How are you doing?
- How are you getting on?
- What’s cooking?

Response
- Very well, thank you.
- Fine, thanks
- Not so bad
- Quite well, thanks
- Oh, pretty good
- Very good
- Well thanks
- Not so well

Farewell
- Bye-bye
- Good bye
- I must be off
- See you later
- I must go now
- See you later / tomorrow / long / tonight
- I must go ahead now
- I’m getting out of here
- I go a first now

Response
- Be good on the way
- Take care on the way
- Keep on the way
- Beware on the way
- I will miss you when you are gone
- Best of luck
- All the best