John Osher is the consummate inventor and entrepreneur. He has developed hundreds of consumer products, including an electric toothbrush that became America’s best-selling toothbrush in just 15 months. He also started several successful companies, including Cap Toys. He built sales to $125 million per year and then sold the company to Hasbro Inc. in 1997. But his most lasting contribution to the business world just may be a list of screw-ups he jotted on the back of a piece of paper.

“After I sold my business to Hasbro, I decided I’d make a list of everything I’d done wrong and [had] seen other entrepreneurs do wrong,” he explains. “I wanted to make a company that didn’t make any of these mistakes. I wanted to see if I could come up with the perfect company.”

He came up with an informal list of “16 Mistakes Start-Ups Make”-since expanded to 17-that has been used in a Harvard Business School case study, has been cited in many publications, and has become a part of what he teaches budding entrepreneurs in his frequent university lectures. He also used the list when he developed Dr. John’s SpinBrush, a $5 electric toothbrush that he sold to Procter & Gamble for $475 million.

I asked John to share his list of 17 startup mistakes with us. He graciously agreed.