American entrepreneurship is booming.

An unprecedented 55 million Americans count themselves among the self-employed, and Generation Y, a fully "digital generation," is poised to become "the most entrepreneurial generation ever."

With more small business comes more competition, and both solopreneurs and startup founders will face increasing pressure in the marketplace to push the "next big idea." A great idea is a good start, but it's only that.

Turning that great idea into a successful business for the long-term requires entrepreneurs to shift their focus from the merits of their ideas, to the evidence they get from customer behavior.

The phrase "the customer is king" might be a cliche, but it holds great wisdom for those creating products and services. Far too often, entrepreneurs get swept up in their own ideas and forget to keep their eye on what really matters: the customer.

Consider some of the biggest product flops in recent memory. They all had one thing in common: The customers' needs or preferences were all but forgotten.

Take, for example, Google Glass. In its quest to revolutionize the way we use computers, Google developed the product in a top-secret lab, shielded not only from potential customers but also most Google employees. While Google Glass was admittedly an idea ahead of its time, the customers still haven't come around.

Obtaining valuable customer feedback isn't just about sitting back and listening to customer complaints. It's about becoming actively engaged with the customer, and finding ways to challenge your own assumptions based on the real-world input of customers.

Here are three important lessons on customer feedback and engagement, based on my own experiences:

1. Customers don't always tell you what they want in words.

Often, some of the most surprising insights can come from observing customer behavior.

Two years ago, my team at Intuit noticed that 15 percent of Mint users were hacking the personal finance product to categorize and track business expenses by creating an "Other" category--a feature that hadn't been designed into the product.

We realized after talking with customers that we lacked a finance management product tailored to the needs of solopreneurs (i.e. freelancers, contractors, businesses of one). In response, we built an entirely new product, QuickBooks Self-Employed, catering to this segment of individuals with unique financial needs compared to those of full-fledged small businesses.

2. Customers can help you fix "impossible" problems.

In many cases, the solution to a difficult problem can be found in customer data.

Shortly after launching QuickBooks Self-Employed, customers complained that bank transactions in the product were limited to 90 days of history (a bank requirement) and they needed 12 months of data for tax purposes.

Knowing that we needed more data to make this feature happen, we asked customers to manually download data from banks and send it to us. Once we had a sufficient number of these files, we could analyze them, learn the myriad formats, figure out how to grab the data ourselves, and turn that intelligence into a feature.

Developing the feature took just two weeks, but it wouldn't have been possible if we hadn't obtained this essential customer data from our first scrappy iteration.

3. What customers don't do can be equally important.

Taking notice of what customers are not doing can help identify critical holes in your product offerings, as well as the areas where opportunity is ripe.

For example, my team saw that freelancers were missing out on approximately $7.4 billion in potential tax savings every year by not claiming all of the deductions available to them (according to the United States Government Accountability Office). As a result, we built a new feature called ExpenseFinder that automatically found deductible business expenses.

Helping customers get back money is a sure-fire way to make them happy.

Some additional quick tips to help you on your product journey:

  • If you plan to monetize your product, do it early; it's an easy way to see if you're creating real value before you go too far down the wrong path.
  • Take the time to sit down with customers in-person (at Intuit, we call these "follow-me-homes"). Customers are more likely to be frank and truthful when you meet with them in their own environment and face-to-face, and you'll get important context that's often missing in surveys and polls.
  • Have your entire product team (especially those close to the product development process, like engineers and designers) take turns answering customer support questions. Talking to a real customer about a problem can be scary at first, but solving for issues in real-time will energize your team and you'll find it's a powerful way to feel connected to the customer.