Nowadays people talk about PayPal's founders as prescient geniuses who would inevitably change the world. It was, however, not so obvious that PayPal would taste its first major success by helping people sell Beanie Babies on eBay. But they had a vision, a hope, and the perseverance to try multiple iterations until they got it right.

I would say, as an entrepreneur everything you do - every action you take in product development, in marketing, every conversation you have, everything you do - is an experiment. If you can conceptualize your work not as building features, not as launching campaigns, but as running experiments, you can get radically more done with less effort.

What if we found ourselves building something that nobody wanted? In that case what did it matter if we did it on time and on budget?

If you don't know who your customer is, you don't know what quality is.

The biggest start-up successes - from Henry Ford to Bill Gates to Mark Zuckerberg - were pioneered by people from solidly middle-class backgrounds. These founders were not wealthy when they began. They were hungry for success, but knew they had a solid support system to fall back on if they failed.

Lean thinking defines value as providing benefit to the customer; anything else is waste.

Better to have bad news that's true than good news we made up