New startups are sometimes formed by teams that have known and worked with each other before, and some are formed by teams that just met each other at a founder dating website or event, and decide to work together after just a few weeks.
In either case, getting the team off to a good start where everyone is on the same page is really important.
Two great books that all founders should read are
When you get started with a good friend, an old friend, or a brand new one, these books show why getting explicit agreements, both formal and informal, on a wide variety of issues can be deeply important in the years ahead.
The Founder’s Dilemmas, by Noam Wasserman, is really focused on tech (and similar) startups that take outside financing and are geared towards a liquidity event (a sale or IPO). The book goes into detail, with great examples, of the things that can (and do) go wrong with alarming regularity. It then examines the dilemmas which are created in deciding how to get ahead of these problems and ways to get through the dilemmas to agreements that are clear, fair and workable.
The Partnership Charter, by David Gage, is a more general look at working together (and not just in tech startups). However, it provides a way for partners to think about, and talk about, working styles, values, accountability and responsibilities, future changes in management and structure and many other key issues. There is some overlap with Wasserman’s book, but the approach is different, and worth the time to read as well.
Look at the reviews on Amazon (and elsewhere), buy the books, and read them!