Maybe credits on some student games or films? I want to get an internship, but I don't know what "basic knowledge" studios would want from me.
I would say a working knowledge of the software they use, the gear that they have, etc... a real passion for the industry and the attitude that you are willing to do anything, even clean toilets and answer phones all day, just to to be around the studio. And be up to date on the current events in the industry. Know what is going on and what is relevant.
Be very personable as well. When you leave an interview, you want them saying, "Wow, he was really nice." Not, "Wow, that guy knows so much about gear!" While the second one is nice, you're not there for your knowledge, you are there to learn. They won't want to work with you for what know know, they will want to work with you if you are a nice guy.
Colin's right about the software they use.
Right before I started grad school years ago, I went around to a bunch of studios looking for an internship/apprenticeship. Now, I had a lot of experience in live audio at the time, but none in recording. All but one said the same thing to me: "That's great and all, but unless you've had at least one recording course, how are you going to know how to set up the signal flow."
Years later, I'm still grateful to the one guy who said: "You've got a lot of experience with live sound, so I don't think it will be hard for you to pick up the software side." He gave me a chance, I'm assuming because of my enthusiasm and confidence in my ability to learn. Those were the things that got me in the door.
Having a base knowledge of Pro Tools might have helped me get in the other places, but I think things worked out for the best for me anyways.
I agree with many of the answers here. Having some nothing of the studio, what kinds of things they do and the gear they have will impress them as this tells them that you have done your homework.
After this it is passion, long hours, listening, watching and being patient. Your time will come. Enthusiasism is not running around trying do every little thing, it is asking questions at the right time (over lunch, breaks, lulls in the mix or edit session). There is nothing worse than someone who tries too hard and gets in the way. As time goes on, read up on the stuff they teach you, practice after hours on the gear if they allow you this. This business is a state of mind not just simply a job to pay the bills. Viva Sound!!!