Congratulations! Best of luck to you.
For preparation, I would start by brainstorming answers to possible interview questions. I used this list:
http://forums.studentdoctor.net/threads/ultimate-potential-interview-question-list.719760/ and jotted down a few thoughts for each question. Don't write out word for word what you would say, since you do not want to appear rehearsed, but I found just getting my brain thinking about some of the tough questions was really helpful.
Do extensive research on the school you've applied to. Most schools have a plethora of information on their website. Find out as much about the program as you possibly can, since not only will that help you be able to answer the question "Why [name of pharmacy school]?" but will help you be able help you formulate a list of questions to ask either during the interview (since most interviewers will ask if you have any questions for them) or throughout the interview day. Remember, the school is not just interviewing you; you are also interviewing the school- you want to make sure it's a good fit for you.
Do as much research on the pharmacy profession. Know the role of the pharmacist and the career opportunities available for pharmacists (it's much more then just hospital or retail). What aspects of pharmacy are you interested in? A good tool to assess what area of pharmacy might be a good fit for you is the APhA Career Pathway Evaluator:
http://www.pharmacist.com/pathway_survey. There's a series of questions asking what type of work environment you prefer and personality questions, and it will give you a list of potential matches that might be a good fit for you. The best part is the survey links to very extensive career profiles, so you can read in detail about what that job entails, education requirements (do you just need a PharmD, or do you need residency training too?), and even salary.
http://www.pharmacist.com/career-option-profiles
Make sure you are up to date on any current events involving healthcare. Some current events to look into include: Disneyland measles outbreak (be familiar with the arguments for and against vaccinations), Brittany Maynard (right to die movement), Affordable Care Act (Obamacare), Ebola outbreak, etc. These may or may not come up during the interview, but it's always good to be prepared, and show you are a well-read individual.
Lastly, make sure you are dressed for the part. If you don't have a nice, well-fitting suit, now is the time to go get one. For men, gray or navy suits are the best choice, since black can appear too formal. Make sure you have matching dress shoes, dress socks, a nice button up shirt and tie. You will want to get your suit tailored and pressed. If you will need to travel to your interview, also invest in a good travel garment bag. I would also recommend getting a haircut before your interview. You only have one chance to make a good first impression, so you want to look your best.