Student or Learner
What should be the correct response when someone asks; How do you do?
...And older people may just respond with 'How do you do?' - but this is pretty old-fashioned. In some dialects, the habitual greeting question is 'How do?' - and I've heard non-dialect speakers using this in a jocular way.
In the case of a formal introduction when someone shakes your hand upon first meeting and says "How do you do?" the usual response is "Pleased to meet you." It's also perfectly acceptable to repeat "How do you do" in resonse, or "Hello, how are you?"