Always capitalize the name of the character in the slug.
If an action description or beat separates two character slugs for the same character, write "(CONT'D)" in parenthesis next to the second slug.
Adding "(CONT'D)" indicates that the dialogue is one thought, but interrupted by an action.
If a character speaks but is not seen on the screen, write "(O.S.)" next to the slug to indicate that.
If the character is narrating or giving a voice-over, write "(V.O.)" next to the name.
When a character is on the phone and we only hear the responding voice, through the earpiece, indicate that by writing "(MUFFLED)" next to the slug. (MUFFLED) is also used when listening to people on a television screen or through a radio.
When indicating the style of delivery or tone for a line of dialogue, write the emotion in parenthesis directly underneath the slug. An example is:
TONY
(stammering)
I don't know what you mean.
These are known as "wrylies" and are not recommended when writing scripts, however.