Secondary characters in stories are created for various reasons; most often because it's hard to write a story about only one person (unless you're doing one of those depressing post-apocalyptic things, in which case you can ignore this post.)
A good portion of the secondary characters I read in other writers' work are what I think of as reactors. Is the weary hero having a bad day? In pops his Reactor Good Buddy to buy him a beer and ask him why. Is the antagonist preparing to destroy the world? Over limps his Reactor Igor to hand him the Doomsday Remote Detonator. Is the angry heroine packing her bags to leave town? Her Reactor Best Friend is there to help her stow her toiletries, listen to her rant and reassure her that she's doing the right thing.
This is the biggest mistake I see made with secondary characters, too. While they might be well-crafted as people in an outline, once they appear in the story they seem to have no lives outside of what's happening to the prime time players. Most come off like paperdolls, dressed and posed and about as animated and interesting.
I think a writer should know much more about their characters than the reader ever will. Think about this when you're creating your secondary characters, and especially when you put them into play in your story. They're not just there to react to the protag, they're there to interact. To illustrate this, let's follow what happens in this scene from my novel Evermore:
As Byrne made his way to the stables, he stopped every man of the Realm who crossed his path and demanded to know if they had seen Jayr. All of them claimed they had not and offered to look for her. The innocence of their expressions aroused Byrne’s suspicions, and he made a detour to stop at the wardrobe keeper’s chambers.
Farlae came to the door in his shirt sleeves, an open bottle of bloodwine in his hand. “May I be of service, my lord?”
“You can tell me where Jayr is,” Byrne said. “Dinnae not bother to deny that you know. Nothing happens under my roof that you or your spies cannae see or hear.”
“I know that Jayr went into the city early this afternoon. Just as I know that you spent most of the morning sitting outside her bedchamber door.” Farlae propped himself against the doorframe, his one black eye glinting. “As does, I daresay, the entire jardin. Doesn’t seem like a very comfortable spot. Is there something amiss with your own bed?”
Byrne’s lips peeled back from his teeth. “What business is it of yours what I do? I am master here. I will take my rest naked, on the battlements, among a herd of goats if it pleases me.”
Farlae shrugged. “Goats are overrated, or so I have heard. Sheep, now, they are said to be quite another matter. I may have to investigate that myself.” He drank from the bottle.
This scene is in Byrne's POV, so his problems dominate the situation. However, Farlae is getting drunk -- or trying to -- and being insolent versus sympathetic to the lord he serves. As the scene progresses, we discover that not all of that has to do with Byrne:
Killing his wardrobe keeper, Byrne decided, would not take a great deal of effort. The hall held at least twenty objects with which he could end the man’s existence. Only the prospect of Rainer’s weeping held him back. “Why did Jayr go to town?”
“Deliveries held up, damaged goods, paperwork to be signed, feed deliveries rescheduled, the usual,” the wardrobe keeper said casually. “I hope she remembers to pick up the parts that came in at the Singer Center for my serger.” He thought for a moment. “I believe a week ago Rain requested Jayr order four gallons of latex paint from the hardware shop. It seems he tired of the colors in his rooms. Too bad he won’t be here to repair them.”
“These errands could be handled by anyone. These are the last days of the tournament; Jayr knows she is needed here—” Byrne stopped and gave Farlae an incredulous look. “You did this deliberately.”
“The serger failed on its own,” Farlae drawled. “I will need it repaired if I am to tailor all that Lycra the humans must have for their Spring season costumes. I had nothing to do with the paint order. Rain is gone off with Viviana. Good riddance.” He took a drink from the bottle.
Farlae is concerned about how Byrne is treating Jayr, but he's also miserable over the fact that Rain, his lover, has apparently run off with a woman. The combination makes him bitter and sarcastic. Meanwhile, Byrne doesn't help matters by getting angry with Farlae:
Byrne stabbed a finger in his face. “This nonsense was but an excuse to send her into the city. You did this to keep her away from me.”
Farlae lowered the bottle and smiled. “Perhaps we did this to keep you away from her.”
“You’ve gone mad,” Byrne said blankly. “Every one of you. My own men, rebelling and conspiring against me. In my own keepe.”
“Doubtless we are.” Unimpressed, Farlae studied the condition of his nails. “Will there be anything else, my lord?”
“Get stuffed.” Byrne walked away. “No.” He stopped and turned around. “Call Jayr on the contraption she hangs on her ear. Tell her I command her to return to the Realm and report to me at once.”
“Oh, dear.” Farlae held up a familiar-looking device. “Do you mean this contraption? I fear in her haste to go, it fell out of her pocket and into mine. Well, Harlech may have helped it get there.”
Byrne grabbed it and threw it against the wall, where it exploded into a hundred fragments.
“That,” he said, staring into Farlae’s black eye, “is what happens to man’s head when I lose my temper.”
“Indeed.” Farlae folded his arms and looked interested. “What happens to a woman’s?”
For a long time Byrne stood and said nothing, saw nothing. For his insolent wardrobe keeper’s questions explained everything. He had lived with these men, trained with them, fought besides them. They were loyal to him because he was suzerain, and they lived by Kyn rule. Some of them admired him. Most of them feared him.
They were loyal to Jayr because they loved her.
“I would never hurt the lass,” Byrne said.
Farlae’s mouth took on a faint sneer. “That is not what I saw last night, outside the ballroom.”
Byrne is shocked to find out that his own men are actively protecting Jayr from him. Farlae witnessed what he thought was Byrne manhandling Jayr the night before, and he doesn't approve. The characters' emotions are at an explosive point now. So, naturally, they both explode:
“I kissed her,” he roared.
“You terrified her,” Farlae shouted back, smashing the bottle of bloodwine against his doorway. “You see, my lord, you were not the only one tracking last night. So tell me, when did your seneschal become your prey?”
“I love her.”
The three words rang between them, echoing down the hall until the shocking sound of them died away. Farlae crouched and began picking up pieces of the broken bottle.
“Christ.” He knelt to help him. “This is a wretched bloody mess.”
“It need not be.” Something like kindness softened Farlae’s craggy face. “Aedan, if you love Jayr, do not force her into something for which she is not ready. Give her leave to come to you, if that is what she wishes. Give her time.” Sorrow filled his eyes. “God knows, you cannot hold someone you love if they do not feel the same for you.”
And right there, Farlae drops the act and shows his true emotions. He is utterly miserable over losing Rain, and draws on that to warn Byrne not to do something that will drive Jayr away. Byrne responds to that in kind:
There was no more time for this. “I’m riding out to the north side of the lake to meet with Cyprien. Tell anyone who is still interested that I will return in an hour.”
Farlae took the shards of glass from him. “Yes, my lord.”
“And Farlae,” he said, staring into his hellish eye, “Rain has as much interest in Viviana as I do in a herd of goats.”
The wardrobe keeper inclined his head. “Thank you, my lord.”
The key here is balance. While Byrne's problems dominate the scene, they don't overshadow or eliminate the existence of Farlae's problems. Both characters reacted according to their different personal situations. Farlae didn't assume the reactor position of responding only to Byrne's problems; he presented his own in various ways, and in fact drew on his pain to offer advice to Byrne.
Also, note that Farlae didn't offer a long monologue or info dump on his situation. He doesn't have to, because aside from the few hints he drops, his behavior reflects it. He's not reacting to Byrne as much as he's venting anger and misery, most of which is generated not by this confrontation, but by losing Rain.
We put a lot of work into creating our secondary characters, so we should take advantage of them. Don't let yours be mere Reactors to your protag(s). Know who your secondary characters are, what's happening in their lives, what they're feeling and how that motivates them before you bring them onstage. Invest them with as much realism as you can, and you'll never end up with a story about a protagonist surrounded by a herd of paperdolls.
Now it's your turn -- how do you handle your secondary characters? What problem(s) do you most often run into with writing them? Let us know in comments.