Sometimes you don't need to give any feedback, the actor will get it right the second time around.
When you do too many takes, everyone loses their energy. It's good to remind your actors what their character's intentions are.
Be prepared to insist on a certain bit of dialogue when an actor wants to change it. Also be prepared to disregard the script and let the actors be free. Both ways are right, just at different times.
Be direct in what you want.
Don't give too many compliments.
When you've got it, get the actors to do one 'for fun'. This is usually the best take.
Don't allow actors to worry about sound issues or lighting, It's not their job.
Often, all an actor needs is a little tiny insight about their character. It's probably something tiny and obvious that you assume they already know.
Take a short break.
Don't indulge too much in goofing around laughing. Jim Carrey is funny in outtakes, the actors in your film aren't. There's work to do.
Keep a close eye on how awake the actors are. Even the best ones dip in and out of the moment, like a footballer who disappears halfway through a game.