These are all common ways of saying "hello" in English and some possible responses:
-Hey ... Hi
-What's up (wassup)? ... Nothing much, how bout you?
-Hi ... Hey, are you good?
-How's it going? ... Good, and you?
-How are you? ... I'm doing great, how bout yourself?
-Yo ... Wassup?
Now these responses are not REQUIRED by any means, but they sound normal to me as a native speaker. Also here are some common goodbyes as well:
-See ya, see ya later
-Later
-Peace out, peace
-Bye