Ask questions. Over the course of the summer and even now, I have been interviewing people applying for an internship with me. Other than the general stuff you should already know, and what Fatbooty said...I will say again, know as much as you can about the company and ask some freaking questions. It was really annoying when I ask if they had any questions and they said that they didnt. All while I deliberately excluded some important information. I've even had people come in and not even know what the internship is about...they were just looking for any job. Uhhh yea...that aint going to work.