How do you prepare for an internship?

I have my first internship this summer with a pretty well known company. My major and focus is Chemical Engineering. I am really nervous. Mainly nervous about being unprepared or not as knowledgeable as they would expect me to be?

For anyone who has had an engineering internship, can you provide and tips or just talk about your experience? How would you have prepared for the internship knowing what you know now?