Whether you are producer or director, one of the biggest mistakes you can do on a set is to publicly give a direction or a note. Particularly with directors, if you need to give a direction to your actor, you always want to get up of your directors chair and approach the actor and give him the note face to face so that nobody else can hear it. The days of the directors sitting on high chairs with mega phones are over. Actors are put in the most vulnerable position on the set out of anyone and you as a director want to make them feel secure in their craft. Never scream out a note. Never give a direction that everyone can hear. Then what happens is people start to judge the actor and the performance and because the actor is aware of this, it will undoubtedly affect his/her performance.
Same thing goes for key crew members. If you have directions or instructions, always pull them aside and tell them privately. This will always make for a better tone on set because it makes the crew feel that their work is respected and valued. TRUST ME!
A studio film director once told me, the best directors and producers are the ones that are able to EMPOWER all the creative people they work with in a way that makes them all feel like the project belongs to them.