The Ultimate Guide to Asking the Right Questions in Investment Due Diligence

Introduction

When it comes to making high-stakes investment decisions, asking the right questions can make or break your returns. Whether you’re looking at a public company or a private equity deal, primary research—talking to the people who know the business best—gives you the edge.

Here’s the problem: most investors don’t know how to ask the right questions.

It’s not just about talking to customers, suppliers, or former employees. It’s about knowing how to extract insights that move the needle. Investors who do this well consistently uncover information that others miss—often the kind of insights that drive multi-million-dollar decisions.

So, how do you do it right?

This guide breaks down the most effective questions to ask in investment due diligence, categorized by who you’re speaking with. Plus, I’ll share uncommon, high-impact questions (including the killer question that reveals unexpected insights) to help you uncover real value—or avoid a costly mistake.

Why Asking the Right Questions Is Critical in Investment Research

Investing without the right due diligence is like playing poker blindfolded.

Consider this:

• 70% to 90% of M&A deals fail due to poor due diligence. (CFA Institute)
• 83% of private equity leaders say their due diligence processes need improvement. (Bain & Co.)
• Top investors like Warren Buffett, Peter Lynch, and Phil Fisher swear by primary research—direct conversations with people in and around a company—to validate or kill an investment idea.

But here’s the catch: not all questions are created equal.

The best investors don’t ask generic questions like “What do you think of this company?” They dig deep, ask unexpected questions, and probe for hidden insights.

That’s where investment experience comes in. Seasoned investors know what really drives value, what signals trouble, and how to read between the lines.

The Art of Asking Killer Questions

One of the most effective questions you can ask across any interview type is:

“What has surprised you (good or bad) about X?”

This question is gold because:

• It gets people to reflect deeply.
• It uncovers gaps between perception and reality.
• It often surfaces insights that no other question would reveal.

For example, a former employee might say, “I was surprised by how often management ignored red flags in the financials.” That’s a huge warning sign.

A customer might say, “I was surprised their product was worse than the marketing made it seem.” That could signal churn risk.

This single question often leads to breakthrough insights. But it’s just the start.

Now, let’s break down the key questions to ask, depending on who you’re talking to.

Former Employees: The Insider Perspective

Former employees know the truth about a company’s culture, management, and execution. They don’t have the same incentives to sugarcoat things as current employees.

Best questions to ask:

• “Why did you leave, and what does that say about the company?”
• “What was the biggest challenge X faced, and how did leadership handle it?”
• “How did working at X differ from your expectations?” (Surprise question in disguise!)
• “If you had to bet on X’s future, what would you say?”

Former employees give you inside knowledge on strengths, weaknesses, and potential red flags—all things you won’t find in an earnings call or investor presentation.

Customers: The Voice of the Market

Customers decide whether a business thrives or dies. If they’re happy and loyal, revenue is durable. If they’re leaving, the business is in trouble.

Best questions to ask:

• “What made you choose X over competitors?”
• “If you could change one thing about X, what would it be?”
• “Do you plan to continue using X? Why or why not?”
• “What has surprised you about using X’s product?” (Again, the surprise factor digs up real insights!)

Customer insights reveal competitive positioning, pricing power, and potential churn risks—key drivers of valuation.

Competitors: What the Market Really Thinks

Competitors love to talk about each other. They know where a rival is strong—and where they’re vulnerable.

Best questions to ask:

• “Which of your competitors do you respect the most, and why?” (If they name X, that’s a great sign.)
• “If you could eliminate one competitor, who would it be?” (This reveals who’s actually winning the market.)
• “What’s something X does better (or worse) than the industry norm?”
• “What recent move by X surprised you?” (There it is again—this question never fails!)

Competitor insights help you benchmark the target company and spot industry trends others may miss.

Suppliers: The Hidden Weak Spot

Suppliers see things investors don’t. They know if a company is financially stable, if they pay on time, and if they have leverage in negotiations.

Best questions to ask:

• “How reliable is X as a partner?”
• “Have you noticed any big changes in their order volume or payment behavior?”
• “Compared to other companies you supply, where does X rank?”
• “What has surprised you in working with X?” (Are you seeing the pattern yet?)

If a supplier says X is struggling with payments, that’s a major red flag investors need to know.

Industry Experts: The Big-Picture Perspective

Experts know the industry inside and out. They can validate whether a company’s strategy makes sense—or if they’re on the wrong side of a trend.

Best questions to ask:

• “What are the most important trends in this industry right now?”
• “What separates winners from losers in this space?”
• “How does X compare to the best-in-class players?”
• “What’s something new investors often misunderstand about this industry?”

Industry experts provide critical context so you can assess whether X is positioned for growth or about to get disrupted.

Uncommon But High-Impact Questions

Beyond the standard checklist, top investors use unexpected questions to uncover insights that others miss. Here are a few:

• “If you were CEO of X tomorrow, what’s the first thing you’d change?” (Reveals major weaknesses or opportunities.)
• “What’s the one thing about X that nobody is talking about, but should be?”
• “Who else should I talk to in order to really understand X?”
• “What could cause X’s success to suddenly unravel?” (A great way to uncover hidden risks.)

These kinds of thought-provoking questions force interviewees to move beyond canned responses and share what really matters.

Why Investment Experience Matters in Primary Research

Asking the right questions isn’t just about having a list. It’s about knowing what actually drives value.

Experienced investors:

• Know which variables truly move the needle in an investment.
• Read between the lines—spot hesitations and vague answers.
• Ask dynamic follow-ups that drill deeper.

This is why top hedge funds, PE firms, and asset managers prioritize primary research. They don’t just rely on data—they go straight to the source to validate (or kill) their thesis.

Final Thoughts: Turning Insights into an Investment Edge

The best investors don’t just analyze numbers. They dig into the reality behind the numbers.

By asking the right people the right questions—and pushing for real insights—you uncover the hidden risks and opportunities that others miss.

And that’s how you get an edge in investing.

Start applying these questions in your research, and you’ll start making better, smarter, and more informed investment decisions.