Other ways to say “How are you” and the difference between “how are you?” and “whats up?”
What’s up is the same as what’s happening. Depends on the certain situations, there are many ways to express How are you! For example, is everything Ok? How is your life? Or even are you Ok?
Thanks Wanderer for your examples. Could you be kind enough to tell me how to response to “what’s up”? Many thanks.
BTW: I wonder if anyone would say “how do you do” when they mean “how are you doing”. It seems to me that this expression appears only in my text book. 
The main problem people have with “How are you?” and “What’s up?” is how to answer.
I usually tell my students that a couple of good answers to “How are you?” are “great”,“pretty good”, “not bad”, “so-so”, “not to good”, and terrible (I think “pretty good” and “not bad” are the most natural). Also a big mistake my Japanese students make is that they always say the same thing everytime, “I’m fine thank you, and you”. This isn’t bad English but if you use it everytime it doesn’t sound natural.
Answers for “what’s up” depends on your situation, sometimes its used as a simple greeting and in that situation I would say “nothing much, or not much” but sometimes that person really is asking you if anything new or interesting has happened recently, if something new happened to you then you should say that thing, for example, “I saw the new movie Avatar, it was good.” or " I’m really busy at work lately."
I like “what’s up?” because its easier to start a conversation than just using “how are you?” and in my opinion it sounds a little more natural. Maybe some other teachers can comment but I’ve always had the impression that “What’s up?” is very American sounding , “what’s new?” is a little more international. Both have the same meaning, so go ahead and use both, but also remember it should be used in casual situations not formal.
“How do you do?” is more like “Nice to meet you.” “How are you doing” is like “How are you” or “How’s it going”
Yeah. How to response to What’s up depends on the situations. Listen to what the speaker is saying to you and you’ll find what the response is. Don’t worry much about that.
Thank you so much for such a detailed reply, Boke.
I’m totally with you on this point. That’s a mistake many ESL learners make, not only your students. For my part, sometimes, I just find that I’m lack of words to answer others’ greeting. All I’ve learnt from my text books are: “How are you?” “I’m fine, thank you, and you?” “Me too”.
Thanks again, Wanderer.