During your internship, you'll be evaluated more so on your soft skills rather than technical skills. That means they're always looking at your behavior and attitude. If you're enthusiastic and coachable, you can learn anything that they'll need you to do.
That said, you need to take a good look around at the people and the work itself and see if you'll be happy/content working there. An internship is like a trial run for the company, it's not the end all be all of your career starting point.
Always take notes. For everything. Every little thing.
And remember, you're always going to be your harshest critic... don't be hard on yourself in the beginning. A positive workplace knows that this is your first time working there so they won't hold unreasonable expectations over you.