Preparing for a tech case study interview, any advice?

I'm in college and I have my first interview on Monday. I'm pretty scared because I suck at solving problems on the spot... However, the company that's interviewing me gave me a case study to complete and bring in to the interview to present. It's essentially converting a PDF to tabular format. How do these normally go? As I said this is my first interview so I don't have experience. What kinds of questions do they normally ask? Should I prepare a presentation, or be ready to present my raw code? Would appreciate any advice. :)