Hello;

An-neyong-ha-se-yo . This is formal so, only use it when talking to a stranger, boss or someon who's older than you. 

An-neyong . This is informal so use it when talking to friends/family.

Yobo-Sayo . You use this while answering the phone

You can use Annyeoghaseyo in pretty much any greetings such as "Good day" , "Good evening" and "good morning" 

Goodbye;

An-neyong-hi-ka-se-yo . You use this when you are staying and the other person is leaving.

An-neyong-hi-kye-se-yo . You use this when you are leaving and the other person is staying. I think you can also use this one when both are leaving but, I'm not too sure >.<

Goodnight;

An-neyong-hi-ju-mu-se-yo.

Nice to meet you;

Ban-gap-seum-ni-da.