"What really great companies do, and great startups, is they don't fail fast," Ballmer added. "They modify ideas, they may see their core proposition needs to change, but it's a great team of people that's fired up, that's found a fertile area, and you just keep working it to be successful."
Those who want to set up their own businesses should prioritise tenacity and patience, and always take the long-term view, Ballmer advised.
He's certainly doing that when it comes to Microsoft's own challenges in recent years, particularly around mobile.
"If look at things in last 10 years, it's probably fair to say there are things that did not go as well as we intended them to. We would have a stronger position in the phone market today, for example, if I could redo last ten years. One of things you have to say to yourself is, do you give up?" he asked.
"I believe Microsoft is well enough capitalised that if we don't succeed, our job isn't to give up and go home, it's try to continue the initiative, but catch the next wave of rapid innovation."
The CEO is expecting a whole different set of hardware — potentially wearable — to be defining the next wave of mobility.
"Take the world 10 years from now, do you think we're going to use devices that look like any of the devices we have today? They will change. Whether they will be things we wear on our eyes or in our ears, devices will continue to change. Do you give up if you miss something, or keep investing for next wave?"
Over the course of the Q&A with the business school's students and dean, Ballmer also shared the best and worst pieces of advice he'd received in his career, and handed out his own tips for those looking to found their own companies.
The worst advice he got, said Ballmer, was to not to drop out of college to join Microsoft, given to him by fellow students and Stanford University.
The best was an aphorism from his father: "If you're going to do a job, do a job. If you're not going to do a job, don't do a job. And that is the key of everything."
"If you're going to do something, get it, heart, body and soul. Do it, and really care. Have the sort of brain where you're always thinking about it and worrying about it and caring about it... Be all in or be all out."
Ballmer again counselled against the short-termist view that can sometimes characterise startup culture, saying that being "all in" is only useful if it comes without an expiry date – business founders can't just expect their big idea to start paying off within six months or a year, he added, citing the examples of Microsoft, Google, Oracle and SAP each taking over a decade to hit the big time.
The former Microsoft boss advised students hoping to found their own company to concentrate on the most basic element of business: finding a price and business model that works.
"Understand price. Think about price. Don't ignore price," he told them. Rather than going for the approach beloved by startups and Google alike – make something cool, worry about how to make money off of it later – Ballmer said fledgling businesses must put their bottom line front and centre.
"You take all these fancy classes – people want to teach about marketing, want to teach about finance, now there's a whole craze – teaching about product development, scrum, rapid, innovate and blah de blah. I got to tell you this thing called price is really important – price/business model. I still think people underthink it through.
"You get a lot of companies start that have no business model, you have a lot that start where the only difference between the ones that succeed and the ones that fail is one figured out how to make money because they were deep in thinking through the revenue, price, and business model. I think that's under attended-to generally, there's probably more that can be done outside the school of hard knocks to learn that."
Ballmer also suggested the students turn their attention to learning all types of accounting, joking that had he not dropped out of Stanford, he'd have taken more courses on the subject.
"Pay attention to accounting. I don't just mean in a financial accounting sense... management accounting even more important than financial accounting - really deciding and thinking about what are you measuring, how do you account for revenue, how do you think about cost. It's fundamental."
Knowing how to recruit is also a top skill, according to Ballmer – for small companies hoping to grow, recruitment becomes the responsibility of all staff who are hunting for the most talented people to join their team.
"It turned out the most valuable thing I added to Microsoft was I got the hiring machine going because I had interview for a lot of jobs in college in business school.
"It's life blood, even to my last minute at Microsoft. The last thing I did was a recruiting call," he said.