The secret to success in either:
Enter late. Leave Early.
You're sitting at your keyboard/typewriter/quill pen/whatever. Ready for the day's writing session. Carol suspects Bob's cheating. Something she found in his sock drawer, perhaps. At any rate, Carol is plenty mad.
Do you start writing....
A) When Carol opens Bob's sock drawer? Perhaps dutifully putting away his laundry, perhaps trying to teach Bob a lesson by shoving the dirty socks he leaves all over the house back in the drawer, or maybe just plain snooping?
B) With Carol, alone in their apartment, drinking and clenching her jaw as afternoon shadows slide across the wall?
C) With Bob entering the apartment, beige walls in the purple twilight, a dark and bristling shape in the center of the room?
D) Somewhere in the middle of dinner: a tense and silent meal punctuated by the clicking of fork on plate?
The only right answer is, as late as possible.
In part, that depends a little on Bob's fidelity. If he's an innocent man accused, you'll want to spend more time building up Carol's fury. We'll get a bigger charge when it's cleared up. Or isn't. Comedy or tragedy, I'd probably start with (B).
If Bob's a cheating dog finally exposed, the emotional flashpoint will be the revelation and Carol's aftermath. Depending on Carol's character (tempestuous or calculating), I'd go (C) or (D).
Notice I wouldn't choose (A). We don't need that setup. If how Carol finds the MacGuffin in Bob's sock drawer is important, let's bring it out in dialogue. After all, innocent or guilty, you can bet Bob will fire back with a few counteraccusations of his own.
Or will he? It's your story.
Do we leave the scene on...
(A) Bob's initial reaction?
(B) That loud slamming door?
(C) Bob's long and lonely night on the couch?
(D) Carol's first breakfast alone in the apartment and the painful, silent hole of Bob's absence?
Again, depends. If Bob's guilty as hell, or Carol just won't believe him, take (A). Yes, that's one very short scene, maybe only a few lines. Bob comes home. Carol's standing there with the McGuffin. Bob's jaw drops open. Carol sees his face and knows.
Notice I used entry (C) there? Part of that is, I'm pretty straight-ahead myself. I understand direct confrontation better than keeping my wrath bottled until halfway through dinner. If Carol is the type to do that, well, that's another story...
But if there's still some hope for this fight, if Carol kind of secretly hopes Bob has a good explanation, or Bob desperately believes his lies might work, or if the MacGuffin that's come out isn't the one Bob *really* fears, we need to stay. We need to stay with that fight.
But AS SOON AS Bob or Carol has what they need from the scene, we. Are. Out of there! No need to stay all the way through the last bitter insult.
For that matter, our entire story should be joined as late as possible, and left as early as practical. The Lord of the Rings has been done; we don't need any more 200+ page denouments.
It works for parties, too. Last night was a Gathering of Clan Dynamo, in celebration of the birthday of Papa Dynamo. A little late, we missed the ceremonial goat-throwing.
And after Elderly Aunt Agatha Dynamo drank that third shandy and decided it would be fun to lift that police car, we knew it was time to go!