How do you evaluate performance of your direct reports? How often is compensation reviewed and who make the final decision on any compensation adjustments? What criteria are used in promotion decisions? How and how often do you provide feedback to your direct reports? How often do you have 1:1s with your direct reports and what do you discuss? If there is fundamental disagreement with the team on a technical/design question, how is the issue resolved? When was the last time that happened? Do you still do hands on technical work? What was the last thing you worked on? In your view, what is the primary role of an engineering manager? Do you have hiring/firing authority for the team? How many people on the team were you directly responsible for hiring? What is the attrition rate for the team, the engineering organisation and the company? Have you had to fire anyone? What are the biggest challenges facing your team/the engineering organisation/the company? What have you done to encourage diversity within your team and the company?
The answers to these questions are important, but just having answers indicates that the manager has at least thought about this stuff. Managers who get defensive when you ask any of these questions should generally be avoided.
What is the long term focus of the company? Figure out whether they are champion players, trying to survive, or comfortable and making money. And whether their plans to meet those ambitions are sensible.
Try to get a feel of the culture. Are they more of a family? Are they strictly work/life separate? Are they serious or playful? Does everyone go home at 5? Is everyone on time? Does the company try to bite off more than it can chew? Is overtime common? Do employees own a part of the company (shares/equity)? How many core members are on a part time basis?