Don't spend too much time prepping solo. Rather practice solo a certain type of a case and then practice them with a partner, Repeat the process multiple times
In terms of resources - Start with Case in point, Victor Chengs books and LOMS.
In terms of case types I would start with either market sizing or with profitability cases since they are much easier:
1) In market sizing cases I would try to understand the basic approach:
- How to structure market sizing case
- Key tools (Assumptions, Households, using personal experience, adjustments, age groups, Income split via 80/20, peak / off-peak calculations, replacement rate, using size of the area to calculate markets, calculating adjacent markets, sanity checks, etc).
- How to do math in the case interview
2) In Profitability cases, I would learn
- How to ask clarifying questions
- How to structure profitability cases
- How to work with data (Comparing with competitors, segmentation, historical data)
- How to answer the questions on creativity
- How to provide recommendations
3) Then I will switch to Market context cases (Market Entry, New product, Acquisition, etc). In addition, I would learn how:
- Structure market context questions
- How to analyze graphs and tables
4) After that I would look at other case types: 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.), Cost Cutting, Valuation, Private equity due diligence, Synergies, etc.
Also, I would try to focus on the most common industries in the following priority(sorted by probability of getting a case): 1-retail and CPG; 2-airlines; 3-Telecom; 4-banking; 5-natural resources; 6-tech
Also, several things that you should be doing on a regular basis:
1) Every 10 cases revisit the previous cases and think how you would structure them differently now having the new experience and having solved the new types of cases
2) Build business judgment. Read about different industries and functions. I strongly recommend practice drawing structures for each industry - profitability, value chain, etc . Then I will switch to getting functional knowledge and key concepts in Marketing (Brand and trade marketing tools, etc), Supply chain (Ops metrics like cycle time and throughput time, distribution and delivery specifics, etc), Finance (Basic Accounting and Valuation). Good sources might be:
- Books - one good book about airlines with numbers and industry analysis can give you all needed industry knowledge
- Company reports, equity reports, etc - usually have a good overview of company and industries.One of the best sources to prepare
- HBS cases - quite useful, but not sure if lot's of them available publically. Probably worth buying
Again, every 10 cases revisit the previous cases and think how you would structure them differently now having the new knowledge
3) Practice fast math
- Learn how to multiply double digit numbers (google fast math tips)
- Learn the division table up to 1/11 (i.e. 5/6 = 83.3)
- Learn how to work with zeros (Hint: 4000000 = 4*10ˆ6)
- Use math tools (Mimir math for iOS), Math tool on Viktor Cheng website to practice
4) Read Viktor Cheng Book and listen to LOMS. I recommend to reread the book and listen to LOMS every 15 cases. Every time, having more experience, you’ll be finding something new.