In a formal situation I would NOT expect anyone to say Hi! How's it going? What's up? If they said Hey! I'd raise an eyebrow and walk away. I would NOT be pleased. Formal greetings: Good morning/afternoon/evening. How do you do? (if meeting for the first time)(shake hands while you say it). Hello, very nice to meet you. How are you? Younger people would probably be more tolerant of informal greetings. I'm afraid I do NOT like any stranger addressing me with Hi! or Hey! at any time, even informal occasions. I do not like students who send messages starting Hi there! To me it is just too rude, and presumptive. But I'm an old grizzly bear.

Hello Oliver, The decision on whether to use formal or informal language depends on who you are speaking to. For people you don't know, you should always use formal language and for younger people and friends you can use informal language. (Think Vous and Tu in French) Hello - Formal Hi - Informal Hey - Inf Thanks - Inf Thank you - F How are you? - F How's it going - Inf What's up - Inf What have you been up to? - F Hope this helps Bob