Trust people by default. Trust them until they lose your trust, not vice versa. If you say you're going to do something, do it. Create space for mistakes. The more time you can spend physically together, the better.
How do you find a co-founder and build a great partnership? YC's Catheryn Li (who also built our Co-Founder Matching tool) and Visiting Partner Divya Bhat cover the importance of having co-founders, how to get & vet one, and the ways to build a successful working relationship with them.
Apply to Y Combinator: https://yc.link/SUS-apply
Work at a Startup: https://yc.link/SUS-jobs
Looking for a co-founder? Sign up for Co-Founder Matching: https://www.ycombinator.com/cofounder-matching