For the first three sets,they're very much the same as greetings in ordinary conversations, especially when you introduce two friends to meet. The readings of 'how do you do' depend on different context.
(Sam is a CEO of Nokia and Jack is CEO of Samsung. This is their first time meeting each other.)
Secretary: Sam, this is Jack. Jack, this is Sam.
Sam and Jack: How do you do. :D (They are shaking hands as they utter.) :D
Secrerary: Sam, this is Jack. Jack, this is Sam.
Sam: Nice to meet you. (or pleased to meet you ,glad to meet you.)
Jack: Nice to meet you, too. :D
(After Sam and Jack met for a couple of times, they became friends.)
Sam: Hello! Jack, how do you do? ( How are ya?)
Jack: Can't complain, and you?
Sam: Same here, thanks. :wink:
Do you get the picture? :wink: