As Robert mentioned there's no real shortcut for preparing for PEI. However, here are some tips that I found useful when preparing for my PEI:
1) First off, here are some key things to remember before you start your preparation:
Typically, the PEI interview is 10-20 minutes long.
The PEI interview will cover ONE topic for whole period focusing on a particular skill McKinsey wants to test. You might be asked to recall details down to the conversations you were having, how you felt and why you were feeling like that for any specific point in time during the story.
Questions are often predictable as McKinsey tend to ask similar questions every year which makes it easier to prepare for
2) The skills McKinsey are looking for in the PEI (from their website):
Be sure to develop at least 1-2 stories for each of the skills listed above. Ideally, select stories which can be used to cover more than 1 skill. This reduces the amount of information you need to retain. When developing your stories it's important to consider the following points:
- Timeline - Over what time period did the story unfold? Stories which unfold over a couple of days (or more) are often better than stories that happened over an hour. It allows the candidate to talk through how they reflected on the problem, formulated a plan, made a decision about the best way forward, etc
- Decision making & planning - Stories which include decision making and planning are better as they show the application of skills that consultants use every day
- Communication - Who did you communicate with? And how did you communicate with them? As stated above, it's possible that you will be asked to recall conversations during the interview so do think about what was said beforehand.
3) Create a list of typical PEI questions based on information available on Glassdoor
Think about how you would use the stories you've developed to answer the types of questions listed on Glassdoor. As stated, questions are predictable so practice is key.
4) Practice, practice, practice...
Finally, make sure to practice telling your stories. This will ensure that you are comfortable with all the details and can recall them without any 'waffle'. When giving your response, be sure to spend the majority of the time on the key details (e.g answering the question asked) rather than providing background information to set up the story.
If you have any further questions about PEI please feel free to get in contact.
Good luck with the preparation!