Some companies use case interviews in their selection process in order to test specific capabilities (prioritizing, analytical skills, problem solving, communicating skills, etc.). Case interviews are mostly used in job interviews at strategy consulting firms, but these kind of interviews can be also used in other industries. It is very important to prepare well for the case study part of the interview, because it is hard to do it right the first time.
Luckily, a lot of students and young professionals around the world face the same challenge and ‘case interviews communities’ have been established. For example, at www.preplounge.com , you can find a lot of information and theoretic frameworks which you can use during case interviews. Also, it is important to practice your skills and that’s why you can set up meetings with other students and young professionals all around the world in the ‘Meeting Board’ page using skype. You can do this a couple of times for free and you will get cases to practice from preplounge.
Moreover, Victor Cheng is a former McKinsey Consultant and he knows a lot about case interviews. He founded the website www.caseinterview.com, which helps students a lot to prepare for case interviews. He wrote a book which can be downloaded on this website and you can subscribe for his daily mailing list in which he discusses every day a different topic concerning case interviews (you can also ask questions yourself).
Overall, it is important to have some theoretical knowledge, but actual practicing with others will probably help you the most to successfully complete a case interview. Good luck!