When interviewing customers, finding their pain point, or problem, is key: It will enable you to craft your solution, pitch, and brand. Valuable as finding the pain point is, a surprising number of entrepreneurs mess up the process. In some cases, you think you already know the problem. In other cases, you're not paying attention to the right signs. This subtracts from your precious time and wastes a great customer interview.

To find your client's pain point as quickly as possible, follow these three steps:

1. Ask open-ended questions

Open-ended questions are great for many reasons. The first is that it gets your customer to open up more--a simple yes or no answer won't get you far. The second is that it helps to stop you from asking questions that will seem biased toward your hypothesis. When you speak to customers, you want to make sure they don't know your opinion. This is one of the greatest mistakes startup founders make when talking to customers. They interpret the interview as validation for their hypothesis, ignoring the real message. Make sure your questions are neutral and get your customer talking.

2. Center in on body language

A lot can be discovered by analyzing someone's body language. This is why Steve Blank is a huge advocate of having the founders perform the customer interviews. You just don't get the same value when all you see is the responses on paper. To make the most out of these interviews, pay close attention to the movements your interviewee is making. Does the person's body tense up? Can you see anger in the interviewee's eyes?

I always look for facial expression. On occasion, customers will try to hide the real problem because of insecurity. Or they might give shallow responses because they haven't really taken time to reflect on the answer. To prevent this, look at the changes in their smile and eyes. You'll notice that when their body language changes there is a shift in emotional response. This is the best way to tell if the information you're getting is what you need. People say to find out if someone's telling you the truth, look right into his or her eyes. It's a powerful statement: Remember it when performing a customer interview.

3. Notice a change in tone

The worst downfall of doing customer interviews through cold calling is that you can't see body language. That means you have to focus on tone. When does the customer sound stressed? When you ask how the problem manifests itself, do you notice an increase in passion and anger?

Another thing to look for: What happens when you ask about a solution to the person's problem. Does the idea that a product could reduce that problem make his or her tone upbeat? Once a customer's voice sounds mad or annoyed, you've found the pain point. If the person all a sudden switches to a happy tone when you talk about a solution, you are on your way to finding an awesome business model.

4. The uncomfortable pause

When you first start using this technique, it'll seem awkward. To get your customer to dive past the shallow explanations, try pausing four to five seconds after he or she has finished. Many times, the person will feel the awkwardness from the pause and continue speaking.

While this may seem a little outside of the box, it does wonders for customers who seem to be giving you surface-level feedback. The more you get the client to talk, the further you'll get into the meat and bones of the pain point. Be careful that you don't overuse this. I've had some customers feel weird because it seemed as though I was just never going to speak. But when you think your customer is about to provide you with valuable information, this will help nudge him or her to go the extra mile.