Study real companies — not fictional examples. See what investors were underwriting, what actually happened, which assumptions held, which failed, and what a founder or investor should do differently.
Filter by the mechanism you want to understand.
Pick a case at the moment before the outcome. Write the three decisions you would make with the information available then.
Identify the claim that could most damage the investment thesis if false, then design the cheapest independent test.
Use the facts to write a one-page investment memo. Then compare your thesis with the documented outcome and ask what you missed.