How does on prepare for interviews at consulting firms?

Consulting companies like BCG, Bain and McKinsey have interview assessment along a few dimensions. Problem solving, structuring, leadership etc. Usually the problem solving and structuring is done using cases. A case is a business problem that is being faced by a company and the interviewee is expected to diagnose the issue, and likely root cause. In addition, hypotheses and solutions etc. The leadership evaluation is done using a personal project and being specific about what the interviewee specifically did him/herself.