Many people are confused on "How do you do?" and "How are you?". "How do you do?" is not actually a question, it is another way of saying "Hello". While "How are you?" is a question and the typical responses are "I'm fine, thank you.", "Fine, you?" and "Fine, thanks."

source: http://www.learnenglish.de/mistakes/howdoyoudovshowareyou.htm


-Erica Jiel Yuzon