Conducting due diligence is essential for private market investors looking to invest in startups. The process helps investors understand a company's history, current status, and future plans. Since early-stage startups often lack extensive operational history, the investigation must be thorough yet adaptable. A checklist is provided to guide investors through various aspects, like the founding team, market opportunity, financials, legal structure, and product evaluation. The founding team is a critical area to assess, especially when tangible metrics are scarce. Investors should examine the professional backgrounds of founders, looking for experience in scaling or exiting previous startups. Evaluating the market involves understanding the Total Addressable Market (TAM) and conducting a SWOT analysis to gauge the startup's competitive position. Financial reviews should focus on historical statements, cash flow, and key metrics like Customer Acquisition Cost (CAC) and Lifetime Value (LTV), particularly for later-stage companies where more financial data is available. Legal and corporate structure is another key area, where investors should review incorporation documents, debt obligations, and contracts to grasp the startup's commitments. The product's current state, technology, and intellectual property require scrutiny as well. Finally, the article suggests that due diligence varies by company stage — from qualitative assessments in the pre-seed phase to more quantitative financial evaluations in Series B and beyond. Understanding these differences helps investors tailor their approach based on the startup's growth stage.