I assume a candidate has at least a basic familiarity with case interview structure coming in.
First, I discuss the candidate's objectives, target companies and perceived weaknesses ahead of our first session. Our initial sessions will focus on structure development, confidence building, and learning from mistakes. We will also set the stage for fit interview responses - over time, we will build a cohesive story that fits with their background, goals and the company in question.
In later sessions, or in individual engagements, I will challenge candidates to go above and beyond a the case's minimum guidelines, challenging them to think about how else they might go about the problem if some key piece of information wasn't present. Similarly, I will push to see how the candidate handles discomfort, or atypical questions, during fit interviews.
All of this feedback will be constructive and positive, and is geared to ensure a candidate is prepared for whatever they run into.