What criteria should founders consider when selecting their co-founder? Are there particular traits or skills that are more critical?
Charles Huang
I think it's important to find a co-founder who can hustle (hustle = build + sell). You need people who can build things quickly and cost efficiently. And you need people who can sell things to different customers or partners. If you have these 2 qualities in your founding team, you have a shot to find PM Fit before you run out of runway.
Kai Huang
A co-founder should have your same level of enthusiasm, dedication, willingness to sacrifice, and be as open minded as you. If a co-founder can't match you in any of these categories, it will be very difficult to work together long term, especially when one co-founder thinks they are doing more than another. Also, they should balance out the team so that if you're technical then you want to find at least 1 business co-founder.
Joseph Hei
One comment here is that if you're truly "co" founders, then they are choosing you as much as you are choosing them. Otherwise you're just hiring them. An underrated quality I think co-founders need is the attitude that they are trying to build on your ideas and efforts, and vice versa — not trying to find holes or blockers in what you're doing. I think startup co-founders need to have an everyday "yes, and…" approach, and fundamentally be optimistic that things can be done.