by Annette Lyon
Characters are the lifeblood of any story. Next to conflict, they're arguably the most important element of your book. The trick is how to make characters that practically breathe on the page, rather than making characters who feel about as lifelike as cardboard.
Listening to characters talk is not only good for showing vs. telling, propelling the plot, and so forth, it's also a terrific way to show characterization. Think of JK Rowling's characters: Hermione sounds very different from Hagrid, who sounds different from Snape, who again sounds very different from Dumbledore. For specifics on writing characterization in dialogue, visit this post about it.
Major caveat here: don't overdo this one. But a specific mannerism or two that a character does when nervous, angry, excited, or experiencing another heavy emotion can add an additional level of realism. An example: In Robert Jordan's Wheel of Time, Nynaeve yanks on her long braid whenever she's angry or irritated. After a while, he doesn't have to tell me how upset she is; I know by how hard she's tugging on that braid.
What is at stake for your character? More importantly, WHY? If your readers know the answers to both questions, they'll be far less likely to put the book down because they're rooting for the fictional people you've created. The characters are REAL. Read Josi's earlier post here for more about character motivation.
4) Point of View
You can reveal a ton about a character by the way they see the other people in their world. Going back to Harry and company, imagine how Snape would be viewed if we saw the story through Malfoy's point of view. Snape would be a hero, a champion, a great teacher. But we see him through Harry's eyes, the kid who gets the short end of the stick from Snape.
5) Internal Dialogue
How do your characters think and feel during and after situations of conflict? What they feel and what they decide to do next reveals more about their character than anything you could tell us outright. When Jean Val Jean releases Javert (and then when Javert kills himself) we learn an enormous amount about these men, and in a more effective way than if Hugo had just explained to us that Val Jean values mercy and Javert is a slave to justice.
Read over your drafts and see how well your characters are coming through. Are they round or flat? Have you shown who they really are? Work in some of these elements so they're just as real to your readers as they are to you.