Under this catchy title, here's a great article by Dharmesh Shah from earlier this month, about the criteria for selecting a cofounder. Dharmesh presents them as minimum criteria - i.e. they all need to be present to make a great cofounder.
I'd qualify that slightly by adding that yes, they should all be present, but they may not all be present right away. This is not to say that you should start a startup with someone if they lack one or more of those attributes - after all, they may never develop those attributes. But be aware not only of the state of your cofounder today, as well as of their future path.
Without further ado, here are Dharmesh's criteria:
- You trust them and they deserve to be trusted.
- They have to be brilliant at building or selling.
- They’re committed to the company, not just the current idea.
- They are likable. You and others enjoy spending time with them.
- They do stuff, not just think about stuff.
- They crank and grind.
- They're reasonable, rational and realistic.