As questions at the interview, EVERY flight department is different. You will probably work about 13-17 days a month on average, with variables. We have 7 "hard off" days per month, 3 weeks vacation after 4 years, up to post trip days for international trips. Ask what hotels they us, do you position overseas business class? What and how are expenses done. Per diem or Actual expenses. Is there a standby policy. How many pilots per plane, are their flight attendants, if it is an international operator on Gulfstream/Global class planes.
Next, ask about a flight operations manual, what it says. Ask about IS-BAO certification, sort of like ISO 9000 for corporate flight ops. If these things are there, good bet it is a first class operation.
Good Luck, GF