Work fucking hard. Work your ass off. Internships are all about proving you are willing to learn, are capable of being in this industry, and could potentially hold down a full-time position—and do a great job. Doing the bare minimum won't cut it.
Keep in mind, there are usually a few interns working in the same department for the same bosses. So you have to stand out. No, that doesn't mean being the loudest or having the strongest opinions. That will attract the wronge type of attention. It may not be immediately obvious that it's happening, but putting in an outstanding amount of quality work will get noticed.