Since you have a very limited period of time here is my advice:
If you have not done any cases yet:
- Take a 1-week vacation to prepare
- If it is not an internship with a dedicated interview period, please reschedule the interview. You can't imagine how many people have failed just because they didn't take enough prep. There is absolutely no penalty for rescheduling.
I recommend the following approach:
1) Start with "Case in point" book - you can download this book for free everywhere. It's not the best guide on how you should approach the cases, however, it will give you the basic understanding.
2) Start practicing cases with partners here or find them locally. !!! Find experienced partners or coaches who can provide a good feedback!!!
3) Purchase and read Viktor Cheng Book (Amazon Kindle store) and listen to LOMS (his website).
4) Start with the following cases (relevant for ATK) and apply some high-level recommendations on structuring:
- Market sizing - structuring from the supply or demand side. Structuring using a formula or using an issue tree
- Profitability - basic profitability framework. Remember about different revenue streams and product mix
- Market context cases (Market Entry, New product, Acquisition, etc). Always start with the big picture "market". Finish with something specific to the case (e.g. How to enter?"). Structure it as if you are defining the work streams for the real project.
- Operational math problem (e.g. Should we increase the speed of an elevator or just buy a second one? How should we reduce the queues? Etc.) - Structuring as a process / value chain, with inflows, operations, and outflow