What makes a good collaboration between admins?

When two (or more) admins team up, it can either go really well — or fall apart fast.
So what actually makes a good collaboration between admins?

Is it about clear communication, shared goals, trust, or just finding someone whose workflow matches yours? Have you ever teamed up on a project, event, or even merged communities — and what did you learn from it?

Let’s hear your experiences and thoughts. What makes a partnership between admins actually work?