I was not formally trained as a director.  But I did have an interesting and excellent education in the craft.  I worked in the theater as a composer for many many prose plays. I started while still an undergraduate and continued working with directors in the professional stage. For over ten years I worked with directors that didn't have a clue about how to work with an actor on the practical sides of the interpretation of a part.  Directors that spent rehearsal after rehearsal acting out each line and expecting the actors to copy their second rate intonation and gesture.  Not all were like that, but all too many were.

I developed a great desire to have my work as a director be as transparent
as possible. I am a minimalist as a director. Get the actors on the stage.
Have the minimum of costume and set. Have them well prepared and let them
do their art and through them have the playwright speak.

To put this as an aesthetic statement:

The playwright should be allowed to speak through his text and stage directions.  The job of the director is first of all to 'find' the play and not create his version of what he thinks it might be.

The actors must be allowed to follow their craft and be helped in the creation of their characters but never feed a line or a gesture [sometimes in comedy with young actors you might show how a fall might be executed or a double take].  

Actors are artists and not puppets.  And the best criticism of the play is one which complements the playwright and the actors and forgets that a director was there at all.

In my extensive work as a director of my own plays for radio I have tried to
follow this path. I am pleased when the acting is praised, the music - if
there is any - and the play itself while my work as a director is forgotten.

I like the feeling that the play directed itself and that the realization is a
natural consequent and not disturbing.