Be prepared to sell their items to the manager
Make sure you have all your answers ready and be prepared to ask questions. Its a retail job remember, so how you present yourself is crucial. Your expected to be stylish and well groomed - this is the first thing they notice.
Research the company, make sure you know what some responsibility would be before you walk into the interview. LOOK GOOD for your interview, you are here for a FASHION job not a sweatpants and sweater job. Be professional with your answers, and avoid trash talking any previous employment as it looks really bad on you.