What is the proper way to use a BEAT in a scene?

Would I include it with the other action like this:

Bob sits down beside Mary. BEAT

BOB
I'm sorry I ran over your dog.

Or on a separate line like this:

Bob sits down beside Mary.
BEAT

BOB
I'm sorry I ran over your dog.

I put it in brackets inside the dialog. Like:

Bob sits down beside Mary

BOB
(beat) I'm sorry I ran over your dog.

But usually inside the dialog not on the beginning on it, only where it's absolutely needed to accent something or make a pause. most of the times it's up to actor or director to make the beat.

It's parenthesis isn't it? Or, you could use a pause?

Bob sits down beside Mary.

Pause.

BOB
I'm sorry I ran over your dog.

It's in parenthesis.

BOB
(beat)
I'm sorry I ran over your dog.

^This way is how you do parantheticals. Each thing on its own line.

The other way you could do it is:

Bob sits down beside Mary. For a moment, they sit in silence.

BOB
I'm sorry I ran over your dog.