I have sat on several myself, more for my Technical Role rather than Inter-personal skills which I should admit are not the best.
A lot of what you need to ask or consider will be related to the role, but when it comes to a technical role, sometimes they are the least important questions.
However - do not assume that getting to the interview stage, means they have the skills to do the job. Sometimes it just means they are able to write a document that says they have the skills. I have seen some interviews for jobs that have only had a small number of applicants - pretty much meaning everyone was interviewed, and others that based on resumes were filtered down to a short list - and failed to have the skills. Qualifications doesn't mean they have the Experience or knowledge.
I could easily spend my time and get the Microsoft, Cisco, Apple qualifications - and yet be unable to do many of the key tasks as I would be studying to the test, rather than knowing the systems. And in many cases - the answer for each of them, is the "Microsoft" "Cisco" or "Apple" answer, and when translated into a workplace, not the most appropriate answer. I am not an in depth specialist in any of them, but I can manage an environment and adapt to multiple platforms utilising a mix of all three solutions if it meets the requirements. MCSE or Cisco qualifications while great on paper, don't mean everything. I have asked a question before of a qualified tech - whats the diff between x and y config - one much easier to configure, setup and maintain, and the other and they have been unable to answer what the difference is. Sometimes being able to adapt, to be prepared to look on google and admit you don't know something is better for the role, than having the qualification.
How does someone work, how they think through various tasks might be an example. Give them several tasks with conflicting priorities and see how their train of thought works.