Cast or crew will sometimes argue with a decision you made. The moment you resort to “Because I’m the director and I say so”, your authority is down the drain.
Obviously, first, know your shit.
Learn what motivates your team. Some actors like room to explore. Others will clam up if not given clear guidance. Some crew members like lots of praise. Others will find it patronising and want it assumed that they’re good at their job.
Absolutely ask other departments for input when needed, but even when you’re freaking out, don’t show it. Think of yourself as a captain. When everyone’s scared, you show the way.
Especially to non-creative, but still essential crew members. Everyone is making sacrifices, everyone is important to the shoot. Would their position exist if it wasn't needed?
If someone treats another crew member with disrespect, make it very clear that it's unacceptable. No inappropriate jokes. Nobody yells. Nobody takes it out on the runner.
They will follow you to the end of the world.