Please keep in mind the following points before drafting the questions you may ask your interviewer, and always remember you need to end the discussion on a positive note.
1. Professional Context : Identify questions which have a direct influence on your learning and growth with the firm. Eg. For an experienced candidate a good question can be - Based on your experience with the firm what opportunities do you see for me in terms learning and growth ? Interviewer's response to this question also helps giving you a decent view of how he/she has gauged your experience or candidature.
If you happen to know about the interviewer beforehand through google search, linkedin and you see a common interest area in professional terms then a question around that can also be a smart choice.
2. Personal Context : There is no harm in being frank about your personal considerations becuase in the end your employement has to be of value for both the firm and you. However, you need to construct the question in a subtle and appropriate manner that exhibits that you are open and appreciative of ideas and do not exhibit rigidity.
Identify areas you think are of personal interest/importance to you (in real terms) location, travel, personal interest like community collaboration, etc.
Many a times candidates who have performed well during the disucssion are keen to know by when they can hear from the firm and are open about other options as well and how interested they are to work with the firm and why.
Hope this help. All the best.