Recently, my critique partner Jessica described secondary characters as one of the strengths of my writing. To say the least, I was gleefully pleased. I’ve never been one of those who considers secondary characters plot devices, existing only to move the story along and be quickly forgot. Rather, I treat them as chances for some color and world-building. They may begin in the needs of the plot, but, with this approach, they become a cast I can economically draw on later in the story if the need arises.
With all my characters, both primary and secondary, I begin by asking what the first thing is that strangers would notice. This question is usually enough to make even very minor characters stand out. For example, at one point, my main characters take shelter with a peddlar. Perhaps he has a regular route around outlying villages, but more likely he walks the city streets, since he has a baby. At any rate, what stands out is the way he dresses. He wears a tunics and trews made of strips of the cloth that can be ordered from him. Around his neck hang tiny mirrors. Pins and needles are stuck in his cuffs, and his tunic has dozens of pockets for spices, candies, and other small items. From his hat dangles ribbons and gits of embroidery. In effect, he is a walking advertisement for his wares; you can’t help but see him coming. Nor are you likely to forget him, since he is a cheery sort in his work clothes and is always singing.
Another minor character is the priest of a popular cult. One of his duties is to sacrifice a goat in the morning and evening, and distribute the meat, bone, and blood to the poor. Instead of simply going about his duties, he turns them into a show, carving the meat on a spit like a waiter in a South American restaurant, tossing slices into the air and flipping them into the hands of the next in line. He is an artist and a performer, memorable despite his brief appearance.
More important characters are developed in greater detail. For example, at one point, my main character is in a village where few people speak his language. I needed someone he could talk to, and he needed a smith, so I chose to be economical and combined those two needs into a single character.
But how did this smith get there? I decided he was a prisoner in the last war. The village is barely at the stage of working copper, so, recognizing the value of his knowledge, the locals broke his knees to keep him from running away, much as happened to Wayland Smith in Norse mythology. Naturally, that makes him unfriendly and resentful, although still glad to show off his skill. He is not as talented as Wayland, so he cannot escape by making himself wings, but, he is resourceful, and has rigged up bars all over his smithy so he can get around by swinging on them — an image I had on the bus as I watched people swaying towards the exit, clinging to the safety poles.
Moreover, as a smith he has magical power over metals, so one of his few friends is his professional colleague and fellow outcast the shaman, who is capable of being male or female at will. The two of them have the occasional night together, which means the smith is bi, or at least highly adaptable. At one point, they arrange a liaison:
Shaman: Male or female?
Smith: Surprise me.
In this way, my secondary characters are built up logically, made memorable and fitted into my background and plot. Some might say I do extra work, but if readers enjoy the characters, I consider the extra effort worthwhile. Moreover, later in the story, I have a set of characters that I can re-use, saving me time and reducing the size of the cast while binding the narrative together. For instance, after his initial appearance, I use the smith to help show the range of reactions in the village to the sudden appearance of a magical healing device — he hopes against all advice that his knees can be healed. Take care of all your characters, even the minor ones, and I believe that they will take care of you.