Start with an idea, not a company. When it's just an idea or project, the stakes are lower and you're more willing to entertain outlandish-sounding but potentially huge ideas. With a 'company' you feel pressure to commit to an idea too quickly.

Prefer a fast-growing market to a large but slow-growing one—especially if you have conviction the fast-growing market is going to be important but others dismiss it as unimportant.

Better to build something a small number of users love than something a lot of users like (Paul Buchheit). Don't deceive yourself about whether your users actually love your product.

Once you've shifted from 'interesting project' to 'company' mode, be decisive. Instead of thinking about making a decision over the course of a week, think about making it in an hour, and getting it done in the next hour.

Ignore acquisition interest until you are sure you want to sell. Don't 'check the market.' There is an alternate universe full of companies that would have been great if they could have just avoided this one mistake. In this universe, they're all dead.

The company will build what the CEO measures. If you ever catch yourself saying 'we're not really focused on growth right now,' think very carefully about the possibility you're focused on the wrong thing.

Avoid the kind of stuff that might be in a movie about running a startup—meeting with lawyers and accountants, conferences, coffees, sitting in meetings. Become a Delaware C Corp and get back to work on your product.

Spending more than the lifetime value of your users to acquire them is not an acceptable strategy, however fashionable it currently is.