There are many English expressions for greetings, ranging from informal to formal ones.
· Informal Greetings
o What's up?
o What's new?
o How's it going?
· More Formal Greetings
o Good morning. How are you today?
o Good afternoon. How's everything?
o Good evening. How have you been?
· Greeting Someone You Haven't Seen for a while
o I haven't seen you in ages! How have you been?
o How're things going?
o How are you getting along?
o Long time no see! (Informal)
· Greeting Someone You Are Surprised to See
o Fancy meeting you here!
o Never thought I'd see you here!
o What a surprise to see you here!