What is the proper way to use parentheticals?

Parentheticals (also called “wrylies” or “actor’s direction”) are used to clear up confusion about a line that could be read multiple ways:

COACH FOX

(sarcastically)

Nice throw, Kyle.

They can also be used to indicate who a speaker is addressing:

COACH FOX

(to Tebow)

Get in there already!

You will sometimes see them used to indicate action. This is acceptable if the action is short. (For longer actions, you’re better off ending the dialogue block and putting the action in scene description.)

This…

TEBOW

(putting on helmet)

Halleluja!

…can be replaced with:

As he puts on his helmet--

TEBOW

Halleluja!

Parentheticals are also sometimes used to indicate a pause in dialogue:

MCGAHEE

Tim...

(beat)

...we’re counting on you.

Or with more specific action…

MCGAHEE

Tim...

(grabbing Tim’s facemask)

...we’re counting on you.

The same idea could be achieved by using a line of scene description:

MCGAHEE

Tim...

He grabs Tim’s facemask and looks straight into his eyes.

MCGAHEE (CONT’D)

...we’re counting on you.

Parentheticals should be used sparingly.

In this 2010 blog post, John August takes a look at some professional screenplays, and counts their parentheticals use.