Interaction is composed of dialogue, body language and can also encompass a character’s thoughts. I find this part of character development to be the most exciting because it is the story. After spending time thinking about a character’s physical traits and personality, I finally get to throw him/her into the mix and see what happens.
But to the basics, why is interaction important?
1) Depicts your character through dialogue, action and his/her thoughts
2) Leads/revolves around the climax or theme
As I said in an earlier post once you have a grasp of your character’s personality the exchange between other characters becomes easier because you have a generalized idea of how your character will react. You can work him/her into the plot and manipulate the plot or character how you see fit in order to cover your theme or climax.
A way to develop interaction is to keep your end goal in mind. What are the milestones of your story, and how can you get to them?
Example, The Great Storms:
Milestone–Jeremiah takes Andrew to live in an underground shelter.
How I made it happen–Jeremiah gets a chance when Grandma leaves Andrew for a night to play bingo.
The resulting interaction between Grandma and another character convinces Grandma to leave Andrew with a babysitter. The exchange serves two purposes: a piece of Grandma’s personality is revealed, and she leaves the house.