When introducing a new character into my stories, I ask myself 3 questions and if any of these cannot be answered, I make the decision either to omit the character or to provide scenes which have these areas covered. The answers to my questions are fully explained using the addition of Benjamin, the Belgian shepherd in Precinct 9.
Will the character be instrumental in moving the plot forward?
When adding Benjamin, a.k.a. Benny, to my novel, I didn't have any plot elements set up to justify him, but I really wanted him in it because he's an awesome dog. So I created two plot elements. I had to make sure he will have purpose, he will be responsible for moving the plot along, and his actions will cause a change in my protagonist's journey. They are simple cause and effect elements.
Will the character provide a means to further develop my protagonist?
The relationship a character has with the protagonist is important to me and the more intimate the relationship, the more depth I can bring to both even if the relationship is a negative one. Remember Hannibal Lecter and Clarice Starling in Silence of the Lambs?
Benny doesn’t share a negative relationship with Kelly, but I use him to show how much control she has over such a ferocious animal. He's a disciplined police dog and could bring down any 200 pound man who poses a threat. I consider his role to be the sidekick rather than protector. It's one of many roles I considered in the Writer's Dream Kit.
Will the character remain unchanged at the outcome of my story?
Lots of things happen to characters during the course of a story. Even if I don't make a change for the character, the character changes. They have to for me. Why else have this character come along for the ride? It can't be merely as a form of entertainment.
Things happen. Relationships end. People die. Others fall in love. Something has to happen to every character I introduce or I simply cannot get excited about writing their journey. In my stories, every character has a journey, no matter how minor compared to the protagonist’s.
Why do I do this?
Because I want my stories to feel as if everything I introduce is fully integrated. I don't want to make that mistake of introducing someone for the sake of having a really cool character in my story. I don't want to create any babies, if you know what I mean.
Do you have a process you use to keep your stories tight from the beginning? Maybe you have guidelines and/or standards you pursue. Care to share them? Comments are welcome, as always!