Aaron Marino of alpha m. gives a run-down about job interview prep. As previously discussed, always over-dress with a tie & jacket and arrive 15-minutes ahead of your scheduled interview time. Also, be polished and clean shaven. Make a resume regardless of your job experience and age.
So, how can you be even more prepared? Review the questions that the interviewer could ask you. See the link below. And ultimately, go in with your head up and confident. Firmly shake their hand and look them in the eye. Let them know you are the best person for the job.