Just a couple of expressions to greet your friends in addition to the ones already mentioned:
these ones are less formal if you need to use them with close friends and buddies:
Hi, how's life treating you?...Great!
Hi, how is it going?( very informal) repliy: "Even better yesterday"
Hi, what's new? Not much!/ Same old stuff.
What's up?
What's happening?
What's cooking?
How are things?
How goes the world?/ How goes the day?
Long time no see! (if you haven't seen each other for quite some time)
Good/great to see you!
How are you?...Getting better every minute!
Older, yet wiser and more handsome! (humorous)
So and so = Fair to partly cloudy (also humorous)
