This is a kind of a cross between an essay on characterizing secondary characters—most of the time, the author has a stronger commitment to characterizing her main character(s)/protagonist(s), so I don’t think as much help is needed—and adopting a certain attitude towards characters when writing. Obviously, this attitude is one I find congenial. It won’t work for all stories, let alone all writers. But since I seem to be obsessed with it lately, I thought I’d write a rant about it.
The quickest way to sum up what I mean is to say: consider all characters as people. Not stock types, not plot devices, not mindless, heartless villains, not mindless yes-men of the good characters. That may be the function they have in the story, but when the author confuses their function with their inner selves—as if a villain really were a Dark Lord even to himself, as if the hero’s perception of him perfectly matched the reality of him—I think sympathy has stopped. I find it especially irritating when the author’s willingness to extend sympathy to only a few people morphs into adoration of those people. One of the things that loving a lot of characters can do is prevent you from falling in love with any single one. And I am all in favor of that.

1) Have characters act outside their roles.

Is a character there mainly to be comic relief? Let her make a serious comment every once in a while. Likewise, the dull-witted younger sister normally trounced by the heroine’s wit could suddenly have a snappy comeback. Just about everybody gets one once in a while. It really, really, tooth-grindingly shows when the only person who ever gets to say anything witty in the story is the heroine. It’s even worse when the heroine’s comebacks aren’t that witty, and yet every other character acts as if they are, to the point of slack-jawed disbelief and stammering, stunned babble.
…*coughs* Yes, sorry. This is meant to be a rant on ways of extending sympathy, even to the caricatures that sometimes take the place of well-defined hero/ines.
Try to let the roles be elastic, not plastic. Let people sometimes do the unexpected. It can be as small as a pertinent observation that no one else has thought of, or as large as making the plan that rescues everybody from Great Peril. But it often takes little effort, while hinting at enormous depths under the surface.

2) Try to move in imperfect step with everybody.

This means that you do not believe exactly the same set of things that any of your characters do. This is great. Why? So many reasons. It:

  • Reduces preachiness.
  • Reduces ranting.
  • Allows characters to be mistaken. (Is this ever important for sympathy. See point 3).
  • Allows characters to be right. (I hate philosophical debates in fiction where a character wins solely because the author either likes her best, believes everything she does, or both).
  • Creates ambiguity/a sense of different perspectives. (See point 4).
  • Means no one character in the story is you, thus reduces the possibility of adoration/overidentification/falling in love.
  • Allows a mixture of emotions for the author to feel towards the character, rather than grinding monotony. (I have written characters I was indifferent to and wanted to see get off the page as soon as possible, oh yes. I never want to do that again).
  • Reduces the chance of one character alone becoming such a scene-stealer that the audience just isn’t interested in reading about anyone else.
  • Is much more likely to get you out of Stereotype-Land, peopled with clichés like Dark Lords, sure, but also Abusive-For-No-Reason Parents, Mindless Peasants, Token-Characters-of-Different-Races-and-Cultures, and Peers-Who-Are-Jealous-of-the-Hero.
  • May help authors get over their hang-ups about writing certain kinds of characters.

So, see? Not sharing an exact set of beliefs with any one character is great. Try it today!

3) Flaws are great. Mistakes are wonderful. Yes, they really are.

I’ve ranted before, and at length, about central characters whom the author protects from every possible mistake and negative consequence of their actions, so this point isn’t about them. It’s about the secondary characters (and, very occasionally, main ones) who make mistakes and are treated like rapists for them.
Why? Mistakes are good. Everybody should make them!
Yes, they’re good. They demonstrate flaws and humanity in the characters. They are, quite often, forgivable. (If they’re not, they tend to be crimes, not mistakes). They can change a character’s point-of-view on at least one situation or person and inspire an arc of growth, or grace, or redemption, or downfall. They can indicate fascinating things about the psychology of the person who makes them. In the dreaded middle of the book, they are busy little plot engines. When external pressures would look contrived and you want to avoid tripe like the Idiot Plot and the Big Misunderstanding, a mistake is a natural and internal way to set things moving again. No, they’re not beautiful; but it should be the execution of the story and the plot that’s beautiful, not a character’s every single action.
Try letting a character stand and fall on his or her own once in a while, rather than assuming they’re irredeemable if they do one thing wrong, or insisting it’s always the fault of another person or trauma in the character’s past. That, right there, is trusting both the character and your own skill enough to show that one mistake is not the end of the world. That, right there, is sympathy in action.

4) Relativism is also good.

Of course you can have characters with absolute morals and absolute stands on certain things. But I continue to believe that a character whose perceptions are 100% correct and in accordance with objective reality is a canon Mary Sue. That’s the definition that means more, to me, than all the super-powers, super-beauty, and love interests in the world. A character can have all those and still be flawed and, thus, interesting (though it gets harder as you pile them on; ask Elizabeth Haydon or Laurell K. Hamilton). But make her intuitively right about all events and all persons, and she’s an omniscient plot device, not a real person. (There’s a reason that when fantasy books have gods interact with the story, they’re usually either non-omniscient or prone to giving answers in riddles instead of straight out).
Thus, create ambiguity. The easiest way to do it, of course, is to write from multiple viewpoints, and thus show your audience that Character X thinks very differently about his interaction with Character Y than Character Y does. But that’s not always possible.
This is where another thing I like emphasizing lately, variation in a story’s emotional tone, works together with characterization. If you let secondary characters affect a story’s tone, color the viewpoint’s perception according to the actions or words of other people, then you can show them as having their own beliefs and still write from a limited perspective. And a character going away from an argument with sharp words still ringing in her head will react differently to the next person she encounters than someone always sanguine, thus perpetuating the chain of character interactions down the line. Of course, this takes a viewpoint character who will listen to others instead of, say, closing her ears because she’s decided she knows all about them already. But since many authors favor a protagonist who’s supposed to be perceptive and not completely self-involved, it’s worth a try.
Another way is through dialogue and action. Rather than always summarizing, say, a scout’s report to the general who’s your main character, let him speak it in his own words. Or describe what the lieutenant does in a fight once in a while, rather than concentrating solely on the general’s brilliance. Does the lieutenant have different ideas about fighting than his commander? I bet he does. Are all of them wrong by virtue of being different? I bet they’re not.
Yes, sometimes it’s difficult to do this because you’ve got a really self-involved narrator, or two or three viewpoint characters very like each other, or another circumstance that crowds out ambiguity. But just because the character is self-involved and limited to his own perspective is no reason for the author to be.

5) Have a series of interactions in mind.

Sometimes, I think, the intense protection of a character against mistakes results less from adoration and more from the idea that if a secondary character is more correct (or at least less wrong) than the protagonist, or has a skill the protagonist doesn’t, or gets the witty comebacks sometimes, it will lead to the idea that that character has “won” while the protagonist “loses.”
Oh, bullshit.
That’s only possible if you conceive of a single interaction as determining and dominating all future ones. Why not have a series of victories? The protagonist gets to be right a lot, but not all the time—and especially not in circumstances where she knows nothing about anything. This character you love is very good at what he does, but not equally good at every skill in the field; sometimes, his specific skill-set is required, sometimes it’s not. Sometimes the protagonist has foot-in-mouth disease, just like everybody. Point 3 again, remember? Mistakes are not a plague. They’re part of a life that also includes victories and flirtation and academic conversations and philosophical debates and nasty shouting arguments. There’s no need to fear that someone will “win” forever by virtue of winning once.
Relationships change a lot. So can characters’ relationships.

6) Take an interest.

This is why the times I wrote characters I was indifferent to, or hated to write because they were boring, ultimately led to me abandoning those stories. If you’re only interested in one character, it’s no wonder that she becomes the bright and shining light of the cast and the others fade into shadows, caricatures, or clichés.
So try to have a bunch of people who are interesting. Or, rather, take an interest in them. Say you dream up a sibling for your main character for plot purposes. Well, why should he stay just a sibling? Find out about him. Investigate his past. Know what he does when he’s not interacting with the protagonist.
I’ve heard some people ask why it’s necessary to know these kinds of things. I think keeping yourself interested and sympathetic to more people than just the protagonist is an excellent reason.
Besides, knowing your other people can rev up the plot, spawn new ideas—oh, but Brother Steven would never allow that, so he interferes, so I’ll need to write this—and increase the population of the world, instead of making it seem like your heroes move through an empty world.
One of my favorite moments in the books I read this past year is the one where George Eliot, in the middle of Middlemarch, shifts from the perspective of her heroine, Dorothea, to that of her much older and cramp-minded husband, Casaubon:

“ONE morning, some weeks after her arrival at Lowick, Dorothea — but why always Dorothea? Was her point of view the only possible one with regard to this marriage? I protest against all our interest, all our effort at understanding being given to the young skins that look blooming in spite of trouble; for these too will get faded, and will know the older and more eating griefs which we are helping to neglect. In spite of the blinking eyes and white moles objectionable to Celia, and the want of muscular curve which was morally painful to Sir James, Mr Casaubon had an intense consciousness within him, and was spiritually a-hungered like the rest of us.”

Eliot understood something about sympathy, and how to extend it everywhere.