Mmmm, we didn't interview ours because he was my pediatrician plus others that I know. But I would ask his experience, his availability (ER calls during the night, other practitioners), what hospitals he is affiliated with. Umm sorry that's all I can think of right now.
So fun! First of all, you need to FEEL a connection to the pediatrician. Some of them are so focused on children that they pretty much ignore the parents or treat them like dirt (SOME, not all).
I actually found my doctor after I gave birth. A ped visits your baby in the hospital to make sure they're right-as-rain and to discharge
them. So that's how I found my very awesome, totally chic, African-American goddess of a doctor who is young and on top of the latest medical news. I loved how she treated my baby and how she spoke to me as the PARENT, with respect. She includes me in decision-making, etc.
Ask about how their office works (when can you call with questions, will a nurse get back to me, how long is the waiting time usually, can I space out vaccinations/not have any at all, etc.).
You may also want to know how long they've been in peds (basically ask for their "track record"), their thoughts on vaccines