In one sentence...
Client interview gives you a legal rule and asks you to apply it to a given situation in the most straightforward way.
What is involved?
With only a very brief memorandum outlining the context of the meeting, the competition requires a partnership of competitors who will be required to conduct a successful client interview by adequately establishing rapport, gathering information and providing the client some preliminary advice.
With the facts provided a week before the competition, competitors have 40 minutes to conduct the interview with their client and 10 minutes to privately confer in a post-interview analysis, which should begin with a summary of the interview, state the relevant legal issues to be addressed, and move onto an explanation of the intended course of action. At this point in time the judge will also confer with the client regarding the proposed course of action.
You will not be judged on how much advice you give, but on the quality of your correspondence and teamwork.