This was actually my first ever job interview. While the interviewer did not ask me to bring along a resume, I still brought one with me just in case. This turned out to be a good idea, as a lot of our talking points were about experiences I outlined on my resume. As far as preparations go, I made a list of generic questions that was a safe bet for almost any interviews. These questions included, "tell me about yourself," "why are you applying for this positions," "what are your strengths and weaknesses," and "what is your availability." In addition to that, I also made a list of less common question that might come up in an interview for a customer service position. These included "tell us about a time when you disagreed with a workplace policy and how you dealt with that," "how would you handle a tough customer," and "what is your motto for working in a large team." Before my interview, I ran through each question and thought of potential, appropriate answers. The most important thing is to stay calm and let the conversation flow; don't sound rehearsed. Good luck!
Depending on when you are going to be interviewing for your position (I was in my 2nd year of pharmacy - not yet an intern), the manager is understanding that you're not going to be that experienced of an intern yet. However, my situation was different because I was currently working at a private pharmacy so I did know what my job title entailed. Be prepared to answer the generic questions - what are your strengths and weaknesses (turn your weaknesses into something you're working on), how do you manage a difficult situation, and how do you work in a team. Also make it very known that you are determined to learn from your pharmacists and you want be an integral part of a team.
Be prepared to discuss why you have an interest in working in a pharmacy. You should have a general understanding of what some of the duties include. You also should be prepared to answer questions about how you work under pressure (resolving patient concerns or dealing with an upset customer).
The best way I think anyone can prepare for an interview is to sit down and make a bullet point list of the things you have done so far in life. For example, the schools you attended, the volunteer experiences you did, the jobs you've worked (no matter how small), etc. Then go back and narrow down your list to the items that apply most for retail pharmacy. This means focusing on talking with people, multitasking, time management, etc. It's best of you have a particular story you can recall for each item from your list.
The interview is for them to get to know you as a person. Be professional, but don't forget to smile, be friendly, and have fun getting to know them.