For the actual "interview", the agent swipes your passport through a scanner, to log you into the database, takes your picture, and several sets of fingerprints--4 LH, 4 RH plus two thumb prints. You do a test run on a demo terminal. A CBP sticker is placed on pp. Besides minor conversation, there really is NO interview.
When I got conditional approval, the email asked me to set up an appointment, on the appointment confirmation an exact description of where to go is noted. At the end of the "interview", the agent noted it took 10 minutes (which he thought was fast in light of the slowness of his terminal. [JFK has lots of terminals, CBP for Global Entry was in terminal 4.]
PS: The documentation states that you should bring proof of where you physically reside (rent receipt, water bill etc.) I brought a rent receipt but it was not looked at.
My agent studied my utility bills (I brought both electric and cable/internet/phone) very thoroughly and typed something about each one on his computer.
My "questioning" was mostly conversational (what I do, how I afford to travel a lot as a student [I'm a former airline employee], etc.) with the only "real" questions having to do with why my drivers license was out-of-state and why I had been to one particular Middle Eastern country for a weekend two years ago.