This is the area where I believe I have learned the most over the last few years.
It took me a long while to settle some of my characters, and then even longer to work how they might interact with each other.
I did this by having scenes between them, one on one, that will never be seen or read.
It is far easier to have one on one scenes, an even easier to have scenes with just one character's actions and perspective.
But when you start to get three or four people in a scene (or perhaps, buildings, corporeal concepts, animals; depends what is sentient in your world), it becomes tricky to achieve all the things you need to without losing the reader's attention or creating confusion.
The key is understanding each character's motivation, their voice, and how they would naturally respond to different situations. This takes time and practice, but the investment pays off in creating authentic, engaging stories.
