1. You can use different characters to bring out aspects of the protagonist you want to emphasize to the reader.
Minor characters who have been involved with the protagonist for a long time are carriers of their own history with and memories of the protagonist. Minor characters can reference the past in handy ways that serve the development of the story. They can make observations about the protagonist’s character or predictions about her future.
Because minor characters are fully realized people in their own right, they have their own biases and inner conflicts that color their perceptions of the protagonist. As a result they’ll all have their own individual attitudes towards your central character, and how they act and what they say should reflect this. These differing perspectives can add depth and complexity to the protagonist and flesh out her life so that it seems to extend beyond the pages of the story.
2. You can use minor characters to represent exaggerated aspects of the protagonist’s own character.
Minor characters can serve as symbols of the protagonist’s own shortcomings that she must overcome in order to achieve the story’s goal.
Likewise, you can use minor characters in a way that represents the protagonist’s own potential – characters that the protagonist looks up to or wishes to emulate in some way.
3. You can use minor characters to benchmark the protagonist’s growth.
The protagonist starts out in her “ordinary world”. As she travels through the course of the story, he or she begins to change – but the ordinary world stays the same. The protagonist’s changing perspective on minor characters who populate the ordinary world can demonstrate how the protagonist herself is changing.
Minor characters can also represent the “new world” – or the changed state of being that the protagonist is moving toward. In this case it’s their changing attitudes toward the protagonist that reflects the protagonist’s growth. For example, they might initially resist the protagonist in some way, but then slowly or grudgingly come to accept her and perhaps even start to admire her.
4. You can use minor characters to represent different sides of a choice the protagonist must make.
The protagonist can be caught between different characters who embody opposing value systems. This is a way you can flesh out the theme or premise of your story: by showing whom the protagonist ends up aligning herself with (or against).
5. You can use minor characters as a ‘mirror’ of the protagonist.
A minor character can double the protagonist in some way: they start out in a similar situation, pursuing a similar fate….but then the minor character veers off in a different direction, usually negative, that serves to emphasize just what’s at stake for the protagonist or how she, too, could end up if she’s unable to overcome the challenges she must confront.