how about you？

  问做什么事情，就用 what about you

问怎么样或怎样做，就用how about you

carlos19900105 的例子能说明区别：

例（1）

A：i like english ,chinese and math, what about you?

B：me too。

此例中A 问对方喜欢“什么语言”，即: I am asking "what language", and the question is "about" you --- what language you like。 所以：What about you?

例（2）：

A：i take school bus go to school,how about you?

B：bike。

   上

此例中A 问对方怎样去，即：I am asking "how to go to school", and the question is "about you" --- how you go to school。 所以： How about you?。