Just brush up on your business analysis skills. I would suggest reading some business case studies in a book such as "Strategic Management" by Dobson, Starkey and Richards (2004). Learn some elementary SWOT analysis or something else basic like "Porter's 5 forces", which you can apply briefly in the case study they present to you.When I had an interview (in February), they had a case study on an online Estate Agent, and its market positioning. There was a threat of a focussed new competitor, and your company also had weak internal structure.