Warning: The links in this post lead to tvtropes.com. Do not click on them unless you have several hours to spare.
1. Your Character Should Have a Good Name.
I wrote about this already, but it bears repeating. Pick a good name for your character; you’ll be typing it often. When tempted to give your character an Awesome McCoolname, remember the advice from TV Tropes: “Try to imagine this person as a baby or as a toddler and everyone calling them this. Try to imagine the parents who would name them this.”
I would also caution you to avoid falling into the “the name must mean something” trap. I’ve spent more time than I’d like to admit on babynames.com, looking up names that mean “dark” or “crow.” The most important thing is that the name belongs to the world you’ve created, not that it’s actually Welsh for “raven-haired.”
2. Your Character Should Have Flaws.
Consider Harry Potter. While he does sometimes suffer from Chosen One Syndrome, over the course of the series, Harry evolves from a poor wee cupboard-dwelling moppet to a stroppy teenager and, finally, into a strong, selfless adult. His flaws are never more evident than in The Order of the Phoenix, where he’s frankly kind of a dick to everyone. He can’t get past his hatred of Snape, and his rash decisions lead to disaster.
A well-rounded protagonist should have flaws. And not just quirky little flaws that make the character more endearing to others, but actual personality defects. While I like Grimoire, the heroine of Grey Magic, quite a bit, she does have her faults. She’s conceited, occasionally bratty, and so reliant on her own intelligence that she has trouble admitting when she’s wrong. Her flaws cause her to make mistakes and butt heads with authority figures.
3. Not Everyone Should Like Your Character.
Bella Swan is a crappy heroine, and not just because her only intentional “flaw” is a tendency towards clumsiness. She embodies the Mary Sue, the wish-fulfillment author avatar, where she serves a stand-in for the author’s own fantasies. Stephenie Meyer stated that she purposefully left off physical description of Bella so that readers could imagine themselves in her shoes more easily, so in a way, she’s kind of a meta-Mary Sue.
Every character thinks Bella is the bee’s knees, despite her bland personality and total lack of self-preservation instincts. She’s bratty, bitchy, and boring–seriously, her only interests are “Edward” and “Jumping off cliffs (to get Edward’s attention)”–and no one calls her on it. I had a similar issue with Sydney Sage, the main character in Richelle Mead’s Vampire Academy spin-off series. Even though Sydney is an insufferable prig, everyone loves her and tells her how great she is all the time. It got really irritating after a while.
4. If Your Character Isn’t Likable, They Should at Least Be Interesting.
The protagonist of your story isn’t necessarily the hero. They may not even be particularly likable. But they should be compelling. Ignatius J. Reilly, the main character in A Confederacy of Dunces, isn’t someone that I’d like to share an egg salad sandwich with, but he’s interesting in the same way that Hoarders is interesting.
There are certain character archetypes that make for a bland hero. Luke Skywalker, for instance, isn’t much fun at parties. Not only does he natter on about bulls-eyeing womp rats, but he’s not nearly as charismatic as his comrades. If your main character suffers from Designated Protagonist Syndrome, at least make sure that you have a Han Solo in the mix. Otherwise, you end up with Eragon, and no one wants that.
More like Luke Skywhiner, amiright?
5. Your Character Should Want Something.
If your protagonist doesn’t want something, there is no story. Ideally, this something should be more than a Macguffin, but that’s not a deal breaker. Katniss Everdeen enters the Hunger Games to save her sister. Alanna of Trebond wants to prove her worth as a knight, even though she’s a girl. Percy Jackson wants to rescue his mom from the underworld. Bella Swan wants…a boyfriend. Okay, okay–I promise that’s the last Twilight dig in this post.
The motivation can, and perhaps should, change over the course of the story. In Neil Gaiman’s Stardust, Tristran Thorn begins his journey across the wall in order to find a fallen star. His motivation is simple, if misguided: he wants to impress the beautiful Victoria Forester. Once he finds the star, however, a complication arises. The star is an injured woman named Yvaine. They journey back towards Tristran’s hometown, pursued by witches and assassins, and his original motivation evolves as he falls in love with Yvaine.
6. Your Character Should Change Over Time.
Artemis Fowl begins his literary existence as an anti-hero. In the first book, he kidnaps the character who is arguably the heroine, the elf Holly Short, and holds her for ransom, nearly plunging the world into a cross-species war over his own greed. Over the course of the series (note: I haven’t read the last one yet), he develops a conscience and learns to rely on others. His journey from villain to hero involves a lot of setbacks, and while the seeds of goodness and vulnerability were always part of his character, it took a long time for them to sprout.
Just as your character’s motivation drives the plot, the events of the plot should shape your character in some way. While you want to avoid altering their basic traits and personality, I think a dynamic character, who learns and grows over time, is more interesting than a static character.