If you had asked me a few years ago, I would have advised any writer to keep stage directions to the minimum.
A dramatist who embellishes his text with highly detailed instructions can be viewed in two ways: as a perfectionist who has a precise vision of what he wants or as an insecure individual who has no faith in the abilities of his cast or director to interpret his work.
In the ideal world, a writer is on hand to collaborate with the director and designer on the first production of a new piece. Hopefully, this collaboration is built on mutual trust. It’s assumed that everyone concerned likes and admires the writing to some degree or they wouldn’t become involved (unfortunately this isn’t always the case).
When the writer is actively participating, she contributes to the rehearsal process. In her absence, the text must stand or fall according to its merits or demerits. But, in either case, she must accept she will have only limited control over the interpretation of her work.
I’ve always regarded this as a delicate process and the standard advice I’ve given to students is not to micro-manage. “Bury the treasure” has been my maxim; trust in the sensitivity and judgement of the artists who interpret your work to discover your intentions and make them their own.
As I say: that's what I used to believe. Hard experience has tempered my opinions. Is there such a thing as being too subtle? I never used to think so but I have changed my mind.
The problem is always the initial reader. Sometimes it's an overworked dogsbody who has the job of diminishing the pile of unreadable scripts sent in (I've done this job myself) but sometimes its just anyone in the hierarchy who wont give your work the minimal consideration it needs.
As Alex Epstein says about film scripts: "… Your script will, if you’re incredibly lucky, run a gauntlet of a dozen readers, development assistants, development execs, execs, agents’ assistants, managers’ assistants and actors. All of them are trying to get through a huge stack of bad scripts. They will not give your script the benefit of the doubt … If a line is not blazingly obvious, they’ll just be confused … Confusion is your enemy. Most readers never recover from it, because they will almost never take the time to figure out what went wrong …”
Here’s the problem. If you’re an established writer, when they look at your script, readers will assume that it works. However puzzled they are, they will give you the benefit of the doubt. If you’re unknown to them, they will not only not give you the benefit of that doubt, they will be more disposed to assume that it doesn’t work.
Harsh but true, I’m afraid. That's why I've resorted more and more to signposting
Signposting is something that writers used to do in the good/bad old days. Bernard Shaw, J.B. Priestley, Arthur Pinero were perpetrators; Rattigan and Coward have done it too. It means addressing the reader directly as an entity and either buttonholing them or tipping them the wink that this is a significant moment and, by golly, you better pay attention!
After multiple occasions where readers have misunderstood or completely missed my intentions, I’ve revised my opinion on signposting. Even if you take them out at a later stage, they can be useful in guiding some readers; particularly those who seem to have never seen the inside of a rehearsal room.