The biggest thing to remember is that a manager is a servant of the team. Never the other way around. You enable them to do work. Which means handling information, communicating, helping them communicate, talking to management, protecting them from unreasonableness, setting clear goals, going to pick up the dang pizza yourself so the work doesn't stop, making sure there are long stretches of time to do work,etc. You do more grunt work than anybody and in return leadership happens.
You nailed it. The best manager I had was the one who knew everything about the project, diligently updated all KPIs and not only did normal PM work but went beyond that when needed. I still remember the day when she needed me to work on weekend, she was so apologetic came early morning to pick me from home, dropped me back and always made sure everyone in the team was satisfied. She truly embraced servant-leadership.
