Are you replacing another superintendent or an add on?
How many homes if residential or size of commercial jobs in what price range will you be responsible for?
What is the current construction time for completion that you will need to meet?
Do you know the electrical codes for your state already? You will need to learn the basics for all trades.
Ask building inspectors in the county, city and area he works in, how they like doing that companies inspections?
Ask his other superintendents what it is like to work for him.
Are you just looking for more money or a career you will love to work in?
Superintendents can get calls 24/7. Let everyone know what hours you will take calls.
You will get all the flack from dissatisfied clients and subs, whether it is reasonable or not.

Hope that is helpful to begin your due diligence investigation.