A number of playwrights I know insist on directing all productions of their works so they can steer every detail and nuance. When they don't direct, they get frustrated because the other director has individual ideas and methods that don't always gel with the playwright's original vision. That's part of playwriting. And for me, that's what I exploit to test my own writing. If what I wrote needs my vocal input, then I didn't write it well. If what I wrote can be produced into a show that works, with the only input from me being the script, then I did my job.
I also like to see what ideas the director and the actors will come up with; ideas that may improve what I envisioned, but with a twist or someone's special experience giving them insight into a particular situation or character. Conversely, when I direct someone else's work, I try to do exactly the same thing - add my own perspective into the script.
Internet information abounds for playwrights and actors, costumers and set designers. But resources seem to be more limited for the art of directing. Actually, one of the best books I've come across is called just that, The Art of Directing Plays, by D.C. Ashton, published in 1931 by Eldridge Entertainment House (now Eldridge Plays and Musicals). It's out of print, but the Advanced Book Exchange may be able to locate a copy of it. Other books on directors and directing may be found at Amazon.com.
The Drama League also lists information and programs for directors, as does the Society of Stage Directors and Choreographers.
As with all facets of plays, it is important for a playwright to understand all the jobs involved; it increases the playwright's awareness of what can be done and what should be done in a play. But not every playwright should be a director, just as not every football player should kick field goals. Each job is important and unique. Some people have the ability to do multiple jobs, and while I've been a director, I prefer to be the playwright. But with the experience, at least I know why I choose one over the other. Directing is not an easy job, and I have immense respect for those who do it.
