what's up?= what's going on?天天見(jiàn)的人沒(méi)什么新鮮的啊,就可以說(shuō)not much或者nothing much；或者抱怨一下my girlfriend is pregnant...或者說(shuō)點(diǎn)高興事my girlfriend is pregnant!或者有的時(shí)候就是單純的用來(lái)打招呼,你也可以用"what's up?"回復(fù)他；具體情況具體分析.
How are you?= How are you doing?是問(wèn)你進(jìn)來(lái)如何啊?回答的時(shí)候一般其實(shí)省略了前面的"I'm doing ..."所以可以說(shuō)（包括但不限于）fine/good/well/ok/pretty good/just fine/great/not good/not bad/awful.這些用法我都聽(tīng)人說(shuō)過(guò).之后可以thanks可以問(wèn)how are you?或者you?...或者直接跟人開(kāi)聊近況.看心情.