I called in to the PM at which I wanted a job and asked to speak to the MOD (MANAGER ON DUTY). When he answered, I asked if they had any position openings and if so which ones. I found out they had an opening for the Cashier position, and so I asked if there was a time that I could come and apply. Nowadays, I would bring a Resume, but at the time I was in High School and I didn't think to do that. So I went in (looking professional) and asked the cashier (being friendly and polite) if she could point me in the direction of the MOD. She paged him up and we chatted for a bit about my knowledge, interests, schedule, etc. I will say that even now, years later, that Manager was a spectacular guy. He made me feel at ease and yet was very professional. After our talk, he asked me to fill out an application, but due to my experience with animal training, he also recommended that I apply for another position as well.
Have a few contacts prepared as references, they will call them. Ask the contacts if they are willing to be your reference BEFORE going into the interview or writing them down. (As a reference for some people, I feel less flustered if I know the call is coming, and I can already have things in mind to say about the person.)