What are the top three things every entrepreneur needs to succeed? When asked that question on at the iCONIC conference in Chicago on Tuesday, Mark Cuban made a persuasive case for the importance of sales, self-sufficiency, and preparation. But as he answered other questions on stage with Inc. president and editor-in-chief Eric Schurenberg and Tyler Mathison, host of CNBC's Power Lunch, it became clear that he was a big believer in at least one more.

First, Cuban's top three rules:

1. Sales Cures All

This one is simple, Cuban said. "There has never been a business that succeeded without sales." Entrepreneurs often think they need a business plan or the infrastructure to support a growing company, but really, they don't. They need sales. So get out there and sell.

2. Don't Ask for Help

Given all the conversation about the importance of finding a mentor and learning from others, it was surprising to hear Cuban tell entrepreneurs not to ask for help. And it was clear that he regarded those who wanted him to be their mentor as, basically, whiners. "Dude, get off your fucking ass and get to work," he said. "Figure the shit out.... Part of what's going on in school is everyone is saying, 'Will you help me?' Help yourself." When asked if he had had a mentor, Cuban didn't hesitate before answering no.

That being said, Cuban made it clear that once he invests in a company, he does offer a lot of help. He said he had hired 15 people to work with his companies to get them up to speed and fill in the gaps in the founders' knowledge.

3. Be Prepared

Being prepared is the best way to reduce risk, Cuban said. Everyone thinks entrepreneurship is risky, but he doesn't take risks himself. "When you walk into a room, if you don't know more about your industry, your customer, your business than anyone else in the world," he said, "someone like me is going to come in and kick your ass."

But here's the thing. Cuban had a string of businesses in his late teens and early 20s that didn't foretell how things would eventually turn out for him. "When I was 18, 19, 20, 22, I probably had more failures than successes," he said.

By the time he was 24, though, Cuban continued, he "was pretty much batting a thousand." When asked what led to the turnaround, he gave a markedly different answer from his top three. "I learned how to put myself in my customer's shoes," he said. "I had enough failures that I could walk into any business and say, 'OK, I understand your business. Here's how my software, my services, my support can impact your business.'"

Cuban said he certainly appreciates failure, but he couldn't say that he exactly embraced it himself. "I was living with six guys in a three-bedroom apartment," he said. "We'd buy our $1.29 chicken packs," late in the day, after the grocery store had repackaged all the chicken that didn't sell into cheaper packages. "That's no fun." Still, he said, "Entrepreneurs never die. We're like cockroaches."