Okay, it never worked for me personally, but I swear by it when it comes to directing my characters. Or maybe it’s them directing me, depending on your point of view.
I first learned of this when I decided to write a scene that I knew would not be in my book. I just did it because I was feeling something that day that corresponded to what one of my characters might have been feeling, even though that character’s contrary feelings was not pertinent to the follow-up of that scene. So, I inserted a half-chapter right there where this character and one other could go off by themselves and “have it out”. I very quickly found an anger and feistiness from these characters that I had not seen before, and one of them was representing me.
Now, aside from the obvious call for attention that my own psyche is demanding here (writing is known to go digging around in there from time to time), those two characters really became alive for me. I knew things I didn’t know about them the more I typed. I had to support their argument as it happened, because I needed to know why they felt the way they did. As I discovered where they were coming from, I learned some new background of theirs which had the effect of separating from me somewhat.
I may not have included that half-chapter, but throughout the rest of the book I wondered if I might need to include such discussions between them and therefore had to keep an eye on them. I just never knew until I finished it.
Since that discovery, I’ve done that half-chapter exercise several times. Sometimes I had to force an argument between characters that weren’t previously at odds. I just wanted to see them mad and hear their voice, which had the added effect of giving me experience with their dialogue. It showed me who was upset and for what reason. It also occurred to me that a good argument now and again would be a good bonding experience with the reader if I picked one that they would be behind.
While the argument/half-chapter exercise is one of my favorites, one slight disadvantage is that all those characters think they’re protagonists now.