I actually am rather fond of interviews! I'm not a very nervous person, so they've never really unnerved me.
I always try to remain composed and I attempt to answer questions in an eloquent, professional manner. Furthermore, I think it's important to look the part. As a minor, I always try to dress to the nines and wear articles of clothing that scream sophistication. (I certainly wouldn't want to wear anything that would make me look juvenile.) Typically, I'll wear a dress with a cardigan, do glam makeup, curl my hair, and put on a pair of heels. I will admit that my one weakness is that I have a tendency to be a tad loquacious and sometimes stray off topic. Although, I do think this may work to my advantage as I have primarily applied for jobs in the retail industry and many managers prefer more outgoing, bubbly individuals, such as myself. I have only applied for a handful of jobs and have landed every single one, including my current job. :)
A piece of advice that I'd give to anyone going into a job interview would be to ensure that you retain eye contact when it's appropriate. (Don't stare down your interviewer, but looking someone in the eyes as you speak shows that you have confidence. Looking away may make you seem anxious or unsure of yourself.)
Also, just be yourself. Try to relax, breathe, put a smile on your face and own it! :)