The company cares a lot of digging deep into personal achievement/leadership/teamwork stories. Instead of asking many questions, interviewers ask one main question like "tell me about a time when you dealt with a conflict on a team, how did you resolve it, and what was your process and your impact?" The interviewer will probe as you respond and dig deeper to really see get a sense of your experience. For the case...McKinsey is interviewer led, so expect them to have questions at the onset of the case. Create a comprehensive framework that is clear and logical...it doesn't need to be cookie-cutter, just something that is logical. Go back to aspects of your framework during the process, and keep your discussion anchored to it. Listen to interviewer cues. You will be asked to calculate the market, or to calculate revenue...probably calculating costs and revenues and then coming to a conclusion based on your calculations.