The most important principle: Fairness, and the perception of fairness, is much more valuable than owning a large stake. Almost everything that can go wrong in a startup will go wrong, and one of the biggest things that can go wrong is huge, angry, shouting matches between the founders as to who worked harder, who owns more, whose idea was it anyway, etc. That is why I would always rather split a new company 50-50 with a friend than insist on owning 60% because “it was my idea,” or because “I was more experienced” or anything else. Why? Because if I split the company 60-40, the company is going to fail when we argue ourselves to death. And if you just say, “to heck with it, we can NEVER figure out what the correct split is, so let’s just be pals and go 50-50,” you’ll stay friends and the company will survive.