Various agents discussed what to talk about should you get "the call" as in a literary agent offers representation.
-How do you work/what's your strategy for working with me?
-How do you give me information (e.g. email, phone calls)?
-How do your contracts work?
-What do you envision for my work?
-What is the author-agent relationship?
-What is your plan from here?
-What is it about my book that you loved/connected with?
-What sort of revisions would you suggest for my work?
-What editors do you have in mind for the book?
-How editorial are you?
-What has your experience been with my kind of book? (Note, if an agent has experience in that genre then you want to hear about it; if they're trying to break into that market then you want to learn why.)
Remember when the agent calls, you're not only interviewing them but they're also interviewing you. See how well of a fit the two of you are.