Hi, speakermom:
Congratulations on getting an agent to call you. It sounds like you are well on your way! Many people try for years to get that phone call.

I would ask:
(a) what genre they generally represent;
(b) names of some authors they currently represent within your genre;
(c) publishing houses they like to work with (i.e., some prefer working with Random House, Doubleday, etc... It helps if the agent has personal relationships with some of the big NY houses);
(d) is the agent physically located near the publishers? An agent doesn't need to live/ work in NY to work with the NY publishers, but it sure helps when they can meet for coffee or lunch...
(e) does the agent specialize in particular rights - such as movie, mass paperback, foreign, etc?
(f) ask to see a copy of their contract;
(g) research the fees the agent charges vs those that are standard in the industry;
(h) don't ever go with an agent or publisher who charges to read your work;
(i) long how in business, and then research the Better Business Bureau and writer's resources to make sure they don't have complaints against them; when you're working through an agent, the checks go to them, not to you, so they have to have a good reputation, especially financially;
(j) what is their accessibility? You don't want to be bothering the agent with calls all of the time, but when you do need to talk to him/her, they should be accessible. I know of several agents with answering machines who sit right there at their desk and listen to people leaving messages and then decide whether or not to call them back... It's much better when a live person answers the phone.
(k) what did the agent do before he/she was an agent? Some agents worked for big publishing houses; those are likely to have friends in those houses they can easily call upon...

Those are the ones I can think of right off the top of my head. If anyone else has any suggestions, please add them!

Good luck, speakermom!