Just as you said, be prepared for any type of question. I was always pretty good at interviews and was comfortable with them, but this one got me.... an interviewer asked me to list 3 good qualities I had. I did that easily, I had thought about that one, it had been asked before....but then he asked me to list 3 bad things about myself too. That caught me by surprise. You don't expect to have to talk negatively about yourself at an interview. I guess that was his tactic. I did it though, and got the job. But from then on when I went into an interview I was always wondering if they were going to throw something at me I hadn't expected.
Just be as prepared as you can, know some things about the place you are interviewing to work if possible, be interested and excited about being there, dress professionally no matter what the job is, have a firm handshake, and smile, it will help put you all more at ease. Those are things I would look for if I were interviewing you. Good luck.