Share results (financial and key metrics) with the company every month.
Experience matters for some roles and not others.
I care much more about the growth rate of the market than it's current size and I also care if there's any reason it's going to top out.
Whatever the founder cares about, whatever the founders think are the key goals, that's going to be what the whole company focusses on.
Be suspicious of any work that is not building product or getting customers.
One of the great and terrible things about starting a start up is that you get no credit for trying.