[vanilla]

I have the same problem...
I usually commit my first class to responses to usual small talk questions.
Examples:
How are you?
What's up?
What's new?
What's wrong?
Hey! How ya doing?
What ARE YOU DOING!!!!???

and so on ...

these are things I might ask quickly to students as I walk down the hall so I try to get it outta the way as well as introducing the classroom english in that first lesson AND my proper name (the students are not allowed to call me by my first name)

that's how I handle it...hope it helps!!!

you might also pull it into a health lesson...take teach the greetings and then point out that "hat's wrong" is somewhat different in that you expect bad news or that someone's poor demeanor can be spotted...

then segue into your lesson "my back hurts" or a complaints lesson

PLEASE EXCUSE MY POOR GRAMMAR AND PUNCTUATION