I have read somewhere that "你好" and "你好吗？" are mostly textbook greetings and are not used by native Chinese, at least not on daily basis. I would also find it hard to believe that two friends who know each other for years would still greet each other with 你好！:)
So, what do the Chinese use? For acquaintances? Friends? Relatives? Family? People you've just met? How much does the level of closeness with the other person determine the greeting?