You need someone that behaves like James Bond more than you need someone that is an expert in some particular domain.

The single word that matters most I think to keep the company productive as it grows is alignment.

So you should always stay on top of people's vesting schedules.

Firing people is one of the worst parts of running a company. Actually in my own experience, I think it is the worst.

If someone is getting every decision wrong, that's when you need to act, and at that point it'll be painfully aware to everyone.

Be suspicious of any work that is not building product or getting customers. It's easy to get sucked into an infrastructure rewrite death spiral.

In YC experience, 2 or 3 co-founders seems to be about perfect.