Different Ways of Greeting Someone in English
We greet people in different ways depending on whether we use formal language or informal language. To greet someone in a formal way upon arriving someplace we will tend to say: "good morning", "good afternoon" or "good evening". When we are using an informal way of greeting we tend to say "hi"; "hello"; "how are you"; "what's up"; "how are you today"; "how come I never see you"; "it's been such a long time"; "long time no see"; "where have you been hiding" and "it's been ages since we last met".
Here's a typical scenario of friends greeting each other:
Paolo and Daren meet but Helli joins them later
Daren: Hello Paolo, what's up?
Paolo: Hi Daren, how're you doing?
Daren: I'm alright, and yourself?
Paolo: I'm good, work is keeping me busy.
Daren: That's good, I can't complain either.
(Helli walks past) Oh! I've been meaning to introduce you to an old friend of mine.
Helli: I'm not old, Daren! Hi, my name is Helli and you must be Paolo? I have heard so much about you.
Paolo: Good things I hope? It's nice to meet you, Helli.
Helli: Pleasure is all mine, Paolo.
Daren: What's with the formalities? Just say hi! Helli is one of us! Anyway Helli and I have to go, later Paolo!
Paolo: Later Daren and I hope to see you soon Helli.
Helli: Likewise Paolo!
There are other different ways of greeting that are non-verbal; like a kiss on the cheek if it's a person you know or simply giving them a hug. Greeting is the easiest way to show a person that you recognize them.