Ask about their individual research projects... If you plan on joining a lab, try to join under a graduate student who is doing a project that interests you, regardless of how geared towards medicine you may think it is.
As a researcher myself, I would say that the most important question you could ask would be much time you would be expected to spend in the lab as an undergrad. If you are serious about research, I would put more hours in than they ask (my graduate lab asked undergrads for something like 10 hours a week..not much at all. But the ones that we actually trained to do things put in well over 20 hours/week)... Also, ask what the typical undergrad responsibilities are in their lab? (Dont be supprised if they say wash dishes - theres nothing wrong with washing dishes...I did it for a while as an undergrad and had to work my way up over a couple years).
If you want to show your really interested in the research, ask if they have any publications from some of their projects, and if they do, see if they have a reprint or if they can give you a title/author list so you can go on pubmed and print them out...then read them. Or, you might go on to the PI's website, if he has one, and get a list of their recent publications (its common for them to list them..just not always up to date). If you can get ahold of some papers, read them and then ask questions regarding the actual research..get a feel for the depth of the science that they are exploring. But, most of all, if you do all that, it will show the graduate students/PI that you are really interested in research, and not just a pre-med looking for a year of "research" experience.
