I put in an app and was granted an interview on the spot; as I understand it, though, that's pretty rare. Normally you put in an app and wait for the call. I also only went through one interview rather than the typical two (they needed to hire someone pretty much immediately, so I got lucky). It was casual (dress business-casual or a little nicer); they often tell prospectives to "come in and talk for a few minutes" rather than having a long interview process. It's basic stuff you'd expect--tell me about yourself; what are your plans for the future; can you work nights and weekends. There are a few tossed in like, "Tell me about a time you had trouble grasping a new concept," or asking about problems you've had to solve in the past. Basically, just have a positive attitude and exude confidence, but be polite. The answers don't matter quite as much as your delivery in this case.