So Called Parenthical

Using the parenthetical to say HOW the actor should say the
line isn't a good thing to do. It doesn't matter where you put
the direction, you shouldn't do it at all.

Now this isn't a hard rule that will kill your chances of selling a
script. It's a suggestion by experienced readers, story editors
and many production executives. If you feel you cannot get your
point across without saying HOW the actors says a line, then
use it.

Remember; your job as the writer is to tell your story and tell
it so well that the actor (and director) will know HOW the line
should be said without you telling them how.

For example: You have a scene where Bob points a gun at Sally.
She says "Don't" If Sally is a well developed character and the
scene is clearly written, the actor will already know that she is
either scared by the gun or defiant. The actor will know how to
say "Don't" without you telling her how.

But if it's important to you to use parentheticals to say HOW the
actor should say the line then it's okay to do so. I always suggest
writers challenge themselves to find other ways to get their point
across.

I would say, as with everything, use in moderation.

I used to use them all the time but no longer find them necessary as I've been absorbing the teachings of some of the gurus out there and making better, clearer characters.
It also gives the actor and director more freedom to interpret the script, which will attract them to the script in the first place.
I still use them however if someone is shifting who they are talking to in a conversation and to reduce confusion when it's important who's talking to who... eg:

INT. RESTAURANT

Bill the braggart stares at his soup as his friend across the table munches on some fresh Poutine.

BILL
My god the service is terrible here....
(to a passing waiter)
Waiter! There's a spoon in my soup!
(to friend)
What is wrong with these people...
(to waiter)
I clearly asked for a straw. How am I supposed
to eat soup with a spoon you incompetent boob!

WAITER
I will now shit on your face.

Waiter drops trou, spins a full 180 and launches a rocket-poop into the soup.

BILL
You missed!!!
(to friend)
See? What did I tell you, boobs!

....

That's an excerpt from an un-filmed Orson Welles Shakespeare adaptation. Gotta follow the great ones...

An excellent example, Spatula. It doesn't tell the actor HOW to say
their lines. It eliminates confusion about who the character is speaking to.

Parentheticals are tough for beginning writers. I mostly agree with what others have mentioned in this thread, about moderation, finding better ways to say what you're trying to say, etc.

Also, actors want to act, they don't want to be a puppet.

BUT, the golden rule of screenwriting is to make the script a good read for the reader. You're selling a script right now to be read, not a movie to be filmed or acted yet. You need to keep those down-the-road considerations in mind, but I believe there are times when it's ok to insert powerful emotional responses and actions from a character. The reason being that most who read a script aren't actors, and by putting it right there on the paper you are giving them an inside look at the psyche of the character.

If the script is ever sold, you or someone else can always go back and edit before the script gets into an actors hands (because they would typically cross all of it out anyways).

I also don't have a problem with quick one line actions being inserted in as parentheticals. Note, I would not do this a lot. But its a way I use to cheat. There are times when I want to manipulate the bottoms of pages...either to leave powerful words at the bottom to cause the reader to turn the page, or to play around with white space. Using parentheticals or not using them can be very helpful in those instances.