In the US, "How are you" or "how are you doing" have become common greetings between strangers when the 'how' is stressed. These questions don't necessarily expect an answer. If answered, appropriate responses are "Fine thank you" or "doing well, and yourself?"
If the 'are' is stressed, it can be applied to more personal inquiry about how a persons life is going.
As fdmaxey has stated, how do you do is becoming outdated.