I think the other coaches here are a bit confused by your question.
Yes, you need to prepare for tests LIKE the McK PST. These are known as online assessments. The other Answers are talking about Imbellus, which you do have to prepare for. However, if applying to BCG/Bain you will ALSO have to prepare for their online assessments!
Lucky for you the McKinsey PST, BCG Online Test, Bain SOVA test, etc. are all quite similar so you really can leverage the practice tests for all of them in order to prepare:
The best way is to really find online tests / questions and practice. Regardless as to whether is a new or old test, the principles are mostly the same:
- Time management (need to think quick)
- Business knowledge/context (incl key formulas)
- Critical thinking (answers that are very similar to each other...clues "hidden" in the text)
- Ability to interpret data/charts
Think of it as a merge of a case and the GMAT/GRE.
You need to be clear on some key case-related and account formulas (margin, growth, breakeven, etc) as well as be good at critically understanding the question (including nuance to questions) and parsing through complicated text with a fair amount of distraction.
You'll also need to be good at chart/graph reading.
The (old) McKinsey PST, BCG Online Test, Bain SOVA test, etc. are all quite similar so leverage resources across all of them.
Best Rote Practice
Rocket Blocks: https://www.rocketblocks.me/
Best Practice Strategy
1) Read the Economist (especially the daily graph and Financial Time frequently
2) Ask case partners to focus particularly on your chart-reading skills (i.e. by providing you with cases with many charts) - Bain and Deloitte cases tend to be chart heavy
Graph Interpretation Tips
1) Read the title - and understand it
2) Read the legends - and understand them
3) Remind yourself of the objective / hypothesis in the case, to see where this might fit
4) Find the differences - where does the line graph plummet or spike? Which column is a lot smaller or bigger than the others? Where does change occur? The differences are what matter
5) Talk outloud while interpreting - first, it helps you think and process your thoughts, second, it lets the interviewer provide guidance and course correct if needed.