Students usually take up until the last week or so to do an interview because they are nervous. It is because they don't know what to say or they are afraid that the interviewee might criticize them. There isn't any reason to be afraid! People are not that cruel. Especially someone who would take their time to go out of their way to come talk with you! Whether it is live or e-mail their isn't any reason to hesitate on your thoughts. You should go ahead and speak your mind. Don't hold back. This is an interview after all. You ask the questions they answer. Then when you can, you discuss that topic further. It's a simple three step process. So please try not to be nervous. It will only further change their opinion of you.
All in all, Just Wing It