We say hi, hello or good morning/afternoon/evening. By the way, the one thing which we don't say - at least not with any degree of seriousness - is 'Greetings'.

Those are the formal english greetings and its typical to ask someone "how are you?" or "how are you today" after a greeting a stranger or a passerby. As for informal slang greeting we say "whats up" or "sup?" or " hows it goin". where i live my friends often say "what it is?" which would formally be "what are you doing?" or "what are you up to?" There are limitless slang terms in english depending on where your at and the age of the person youre speaking with. Most languages use english's formal greetings though.

As much as we are creative. Which ones do you already know?