If you never introduce the character, you can use NARRATION as the character name. If you have a specific character, it's useful to list the name.
Code:
SLUGLINE 1
... description & actions
NARRATION
..........
SLUGLINE 2
... description & actions
NARRATION
......
Example with name
Code:
SLUGLINE 1
... Dave is doing something in his office cubice.
DAVE (V.O.)
This is pretty much a day in my life.
Man comes over and yells at Dave.
DAVE (V.O.)
Yep, that's my boss, Mr. Piddlington.
SLUGLINE 2
... Dave at home/bus/etc.
Pacing the voice over around your actions helps to give a sense of the timing of the scene for the voice actor and editing the clips in the scene.
In the rare case you can use a SERIES.
Code:
SERIES OF SHOTS - STORE
A. Entering dept. store
B. Trying on clothes
C. Carrying to the Checkout
D. Ringing them Up
E. Walking towards the exit.
END OF SERIES
DAVE (V.O.)
It seemed like an ordinary day. Picking out
a new wardrobe for work ...
INT. DEPARTMENT STORE - DAY
THREE MASKED MEN run in waving guns and everyone
drops to the ground.
DAVE (V.O.)
... well, it started out that way.
....
Dialogue is best linked to actions inside sluglines but can be used with series. But as you can see above, the series would probably run longer than the dialogue. So to know exactly when you want the dialogue to appear, you'd typically break those out as actions.
Code:
INT. DEPARTMENT STORE - DAY (CONTINUOUS)
FRONT ENTRANCE
Dave enters the dept. store.
Wanders to the the clothing section
DRESSING ROOMS
Dave tries on some clothes.
DAVE (V.O.)
It seemed like an ordinary day. Picking out
a new wardrobe for work ...
CHECKOUT COUNTER
Dave carries to them to the checkout. The clerk rings them up.
FRONT ENTRANCE
THREE MASKED MEN run in waving guns and everyone
drops to the ground.
DAVE (V.O.)
... well, it started out that way.
....
There are other ways people have handled it. My advice is if you have a film that most closely matches what you're trying to do, see if you can get a hold of its script.