If you love novels, you want the stories to include not just the hero and heroine but interesting, entertaining peripheral characters. Will they be friends, relatives, associates, co-workers, clients, customers? Who will be that character - or those - to which the author invests pages of interchanges with the main character(s)?
So much of their composition again depends on the genre.
When the recluse hero of Then . . . you opens the door to the woman who's seeking refuge, the environment he's spent years refining faces immediate change. An interruption so profound, he calls his best friend and mentor trying to articulate his unusual dilemma. That's the first brief introduction to this peripheral character with several more to be added who will fill out the landscape of this story.
What is it you want or expect from the peripheral characters in the novels you enjoy reading?
I know from an author's standpoint, I never know who they will be until they appear in the story and tell me who they are and how they plan to contribute. Sometimes, there are quite a few of them and other times not so many. Some are perfect additions and add a warmth, humor, wisdom, or steadiness when needed. Others irritate, chide, and create disturbances until their time in the story runs out. For this "seat-of-the-pants" writer, I won't know their intentions until they show up.
It's quite a journey to take before "The End".
Father, thank you for this story that really got to me. So much. Thank you is never enough. In the Name of Jesus, Amen.