Within BCG, I have conducted more than 100 interviews (Round 1 and 2) and pass / no pass discussions as part of the recruitment team. Typically, there are a few clear reasons why candidates do (not) get to the next round.
As such, the first thing I start with in the coaching session is an open discussion and assessment of where potential strengths and weaknesses are of a candidate, with a honest assessment of how you'd likely be scored. Based on this, we will have a targeted approach on how we can improve this.