I've had 2 interviews in my whole life. In thefirst I was 15 and the second I was 17. When I was 15 I was all nervous for it. I was mostly just quiet and very polite though. Overall I already had the job so it didn't matter. The second again already had the job but was pretty easy about it. I was tired and came from my old job. They just asked if the job was alright sounding and what hours I'd work. And I just told them anything, since at that point I was spent. They seemed to like my casual yet curtious attitude.