I would recommend you to focus on 5 areas to crack a written case; I have reported them below with some suggestions on how to prepare for each of them
1. Learn how to define a plan of action and stick to that
The first thing you should do in a written case is to define a plan and allocate in the best possible way your time. Assuming 60 minutes for the analysis, a good approach would include:
- initial quick reading – 5-10 min
- structure the approach – 5 min
- make slides/answer to the questions adding detailed analysis and math – 35-40 min
- final review – 10 min
You should then practice to stick to the time allocated, in order to maximize your final performance.
2. Practice graph interpretation
You will normally have to analyse graphs in a written case. The best way to practice is to take graphs from online resources and use a timer to test in how much time you can understand the key message. McKinsey PST graphs could be a good practice for that.
3. Work on quick reading and quick understanding of key information
You will not have time to read and prioritize everything, so you have to understand where to focus. The ideal way to practice is to use long cases such as HBS ones, and practice on reducing the time needed to absorb the key information that can answer a defined question. Quick reading techniques could also help.
4. Practice quick math
You will normally have math to do in a written case. GMAT and McKinsey PST math should work well to prepare on this.
5. Learn how to communicate your slides/answers (if required)
You may have to present your findings at the end of the case. I would apply the same structures of final sum up in a live interview case, that is:
- Sum up the main questions you have to answer
- Present your proposed answer and detail the motivation behind
- Propose next steps for the areas you have not covered
As you will not be able to double check hypothesis with the interviewer as in the live case before the presentation, it could make sense to clearly state when you are making hypotheses and that you will have to verify them with further analysis.
Hope this helps,