I haven't gotten to this point, but having worked at the bedside with many docs you might want to ask about...
On-call (nights and weekends)
Patient limits (how many are you expected to see per day)
Diagnostics (is there a minimum, i.e., labs, EKG, UA...)
Rounding through hospitals (is that your responsibility?)
Surgery (will you be RNFA or no surgical experience?)
ER (will you take call in the ER?)
Some of the basic interview questions have to do with past experience, where you see yourself in 5 years, what your motivation for being an NP...
There are plenty of NPs here who can give you better advice, but these are the few things I've come across through clinicals and the bedside job.
Best of luck to you!