"Have a nice day."
That's what I assume people will end a conversation with. It's not a bad assumption. And, polite guy that I am, I respond back with "you too".
The problem is, my response is automatic. And "you too" doesn't always work. For example, today, when conversations tended to end with "happy birthday". "You too" in that case makes no sense. But twice in less than an hour, I was wished "happy birthday" and responded with a hearty "you too!"