I think one of the major things a director has to do is to know his subject matter, the subject matter of his script, know the truth and the reality of it. That`s very important.
As I`ve always said, preproduction is so important. When you cast the actors, you`ve done much of the work. Now, you may need to guide them a little, take it up or down, have them go faster or slower, but the casting process is crucial.