When attending an interview, preparation is a key factor in learning about the company you could potentially be working for.
There are many avenues through which to source the relevant information. Firstly, ensure you gather as much information as readily available about the position and prepare examples to explain how your skills and experience complement the job requirements. Search online for any information about the company and learn as much as you can about what they do. You may also research who will be interviewing you. LinkedIn is a great place to gather this background information. Finally, go into the interview with some prepared questions. For example, any information you were unable to find about the company, or something additional about the role you need clarification on. Your questions demonstrate your interest in the position and initiative prior to the meeting.
Remember it is important that you end up knowing as much about the company and the role as they do about you so when it comes to offer time you can make an informed decision.