how are you.

I'm fine.

I am fine.What about you ?

I am fine.And you ?

常规来说就一种。 fine . thanks ,and you?
见面的时候，问好的方式都是有很多种。初次见面的。how do you do. nice to meet you. glad to see you.
要是彼此熟悉了。 一般 hi. 就ok了。 要是两人 比较久没见面可以说。how are you doing? 你近来怎么样？ 或者最简单的。long time no see.

根据实际情况回答（熟人）：
couldn't be better. thanks. 好的不能再好了-春风得意啊，谢谢
just so so, and you? 一般般啦，你呢？
can't complain. 没啥好抱怨的了~
not really good. 不太好
（不是很熟悉的）：
fine, thanks, and you? 很好，谢谢，你呢？

Fine,and you ?

I am fine too!