Guys, I have a completely different take on this, which I want to share with you, whether or not you agree. I have been practising as an attorney for more than 8 years now and I hope my experience can be of help.
An interviewer does not want to hear questions such as "Is there any structured training/mentor program?", "How is work assigned?", "What is the hour requirement?", "Is that billable hours or billed hours?" because such questions will just bore them to death and they are not interested in answering those questions at all.
Likewise, an interviewer is not in the business of finding out whether you have "done your research about the firm", because: (1) if they are a practising attorney, they do not have a clue about what is going on in the marketing department, and (2) the image conveyed to prospective recruits by a firm's website and other literature does not give a picture of what the firm actually does but what the firm wants you to think they do. The situation is different though if you are interviewing for an in-house position.
There is only one question that an interviewer (or prospective client if you are pitching for work) wants to be asked: "What are you looking for in a candidate?". All interviewers will love to be asked that question as it will give them the opportunity to tell you what their needs are and who they believe will best meet their needs.
Remember the interview is as much about them looking for candidates as about you looking for work. So please ask questions that are relevant to them as well. And then of course if you really want to know if there is any structured training/mentor program, etc… feel free to ask (but I never do so until a later stage in the recruitment process).
Hope this helps and good luck!
Attorney and author of Soft Skills for Lawyers (www.chelseapublishing.com