4. Only the Director directs the talent.
Other members of the crew should not make suggestions to the actors or chime in with ideas. The Director's job is to get the performances from the cast, ergo if anyone else has a suggestion, it should be given to the Director, who can do with it what she sees fit. This also goes for feedback to the actors about their performance. The producer or gaffer might think the actor's delivery is great, but, again, it's up to the Director to decide if it's right. On the other hand...
5. Actors can give each other feedback.
They need to be able to discuss how their characters are interacting, give each other suggestions, etc.
6. Give Actors space to rehearse.
On a small set there's often no place to retreat to, so the crew should be cognizant that socializing with the cast between takes can rob them of time to run their lines or mentally prepare themselves for takes. On
Polaris, as the A.D., I had to occasionally shoo set visitors away from the cast for exactly this reason.

Give actors a space to work off set.
7. Don't overdirect the cast.
It's usually bad form to tell an actor how to say a line, although some will ask you to if they're not understanding.
8. Direct via suggestion, not specifics.
Most actors I've worked with respond best when I give them something they can work with that isn't overly specific. For instance, in one scene I noticed that two actresses playing bad girls got really close together at one point and threw back their drinks at almost the same time, so I told them to stay shoulder to shoulder, and to synchronize their drinking, but added "play it like you're a two-headed hydra". They got it. Likewise, in another scene a planned bit of business to stop the hero wasn't going to work, so I told the actor playing a bad guy "be the door", and he played the scene so that when he stepped in he basically became a physical barrier. Sometimes I'd just toss them a note about tone, like, "The upper deck of the plane is the mountaintop where the wise Yogi lives, and down here on the lower deck is Hell " which has nothing to do with the plot but gives them a metaphorical idea about how to play the scenes.
On the other hand, some actors might just want to hear exactly what you think you want, and will ask you, "So, show me what you want," at which point you should do so.
9. Don't feel the need to CUT if you just want another go at a few lines.
If the energy is good, it's often better to just say, "Gimme another," or add, "One more, but angrier," or whatnot. But...
10. Don't do "rolling direction".
While it's often faster to "give me another" rather than to cut, it's
not a good idea to get into direction of any complexity while the camera is rolling. If the direction for the next one takes more than 10 seconds to describe, cut, discuss, and start a new take.
11. Have the A.D. announce when each actor has wrapped their scenes for the shoot.
"Attention please. Joe Blow has wrapped his work on ____." It's the moment where they get to be the center of attention before they exit the production.
12. MAKEUP!
Some fan productions skip this. Don't. Cameras are unforgiving, and no one wants to look bad, so make sure you have a makeup person who can buff n puff the cast so they all look good.
13. Be open to suggestion but cautious about changing the script.
Actors will often suggest changing a line so it sounds more natural or makes it easier to say. On the other hand, changing a line without understanding if it has a broader context in the script is dangerous.