How do you come up with a winning business idea?

That’s a question that stumps most aspiring entrepreneurs. In fact, when we ask new Mixergy members what their biggest challenge is, almost one in four say it’s coming up with a profitable idea.

Proven founders have talked a lot about these issues on Mixergy, but there are more than 950 interviews and 160 courses, so it’s hard to track down.

So today we’re highlighting four interviews and two courses about how proven founders generated ideas and picked the one they built a business around.

1. Call Prospective Customers

You’ve probably heard that you can get great ideas from your future customers. But how do you start a conversation with them?

Cindy Alvarez of KISSmetrics used Quora, finding users who posted questions about analytics, then asking them for a quick phone call to learn more about their problems.

Why call instead of email? “If you’re talking on the phone, you can hear when [someone] starts saying, ‘Well, I wish I could do this, but…’” she says. “Also, you can keep asking more about that, so you can get a lot more detail.”

Learn how she asks for the phone call and get the top four questions she asks during the call in her Mixergy course.

2. Become a Consultant

Another way to get ideas from future customers is by becoming a consultant.

Nick Crocker, founder of fitness coaching business Sessions, did that by becoming an exercise coach for his customers. “The real insight [I got was]…the power of human obligation,” says Nick.

But although obligation was powerful motivation, clients didn’t want to have to be somewhere at a certain time. So Nick created a business around personal fitness coaching via email and SMS messaging.

Learn more about how Nick became a consultant and tested his idea in his interview.

3. Go on a Sales Safari

You might be overlooking great ideas because you’re actually too much of an expert. You assume that everyone knows how to use Twitter or set up a WordPress site.

That’s why Amy Hoy of Slash7 goes on a “sales safari” to uncover profitable ideas hiding in plain sight. “Look at the blogs, the forums, the mailing lists, IRC, LinkedIn groups,” she says. “What are people talking about?”

Then, go deeper. “You can’t just look for one question that people ask over and over again,” she says. For example, if a lot of people are asking about how to hire a really good JavaScript programmer, “then that means there are [programmers] who want those jobs but can’t fit those jobs, so they might be interested in learning how to do that,” says Amy.

Learn more about how Amy goes on a sales safari and identifies a good problem to solve in her interview.

4. Look for a Passionate Disgust

Everyone tells you that to come up with a successful business idea, you should follow your passion.

“I freaking hate that statement, to find your passion,” says Erica Douglass, founder of Whoosh Traffic. “Most people’s passions aren’t relevant to anything people will pay for. You really have to find that intersection of what you’re passionate about and what people will actually pay for.”

One way Erica does that is by looking for what she calls “passionate disgust,” or a problem that’s incredibly frustrating to her and to others. For instance, Erica’s frustrations with hosting companies drove her to start hosting websites, which snowballed into starting her first company, Simpli Hosting.

Learn more about how to find a passionate disgust and how Erica makes sure her ideas will be profitable in her Mixergy course.

5. Give Ideas the Profitability Test

Maybe you already have a great idea, but you’re not sure if it’ll work.

That was the case for Joel Gascoigne of Buffer. He had a problem that he thought might make a great business: He wanted to input several tweets once and have them automatically post throughout the day.

But Joel knew from past experience that solving your own problem doesn’t guarantee paying customers. So before he built anything, he put up a page to see if anyone was interested. He collected email addresses, and once there was enough interest, he tapped that email list to get feedback as he built the app.

Learn more about how Joel tested his idea in his interview.

6. Search the Graveyard

Want to develop an app but don’t have your winning idea yet? Great! Gabriel Machuret, founder of Release My App and author of ASO Ninja, says you’re in good shape.

That’s because his most profitable ideas weren’t new ideas, they were old ideas he found in the “graveyard.” Gabriel uses Google Play to search for apps that are no longer updated, but still get downloaded. “The developer gave them up,” he says. “[But] once we know people are consuming in a market, they’re always going to consume,” he says.

So Gabriel makes improvements to the dead apps, bringing them back to life. He shows you how to search the “graveyard” for app ideas in his interview.