I've blogged about the importance of creating a 3-dimensional main character before, but there are lots of other people who populate the pages of a book. Many writers develop a connection to their main characters, the hero or heroine who must go through all the trials and tribulations before they reach their happy ending...or tragic conclusion. But you should spend some time thinking about the supporting cast in your book, too, and make all of them as real as possible.
Who Am I?
With each and every character you create, take the time to think a little bit about who they are. I create a character sheet for all my books, with a brief bio for everybody who's going to appear. The bio tells me what the character's complete name is, what their nicknames are if they've got any, what they look like (and, in the case of the Deck of Lies series, which designers they prefer). But beyond this, there are other important details that writers need to include for many of their main supporting characters. If your main character is going to interact with these people, shouldn't they at least be interesting?
- History. Did this person grow up in a wealthy household, or a poor one? Do they do well in school, or get terrible grades instead? Did something happen to them that shaped them in a significant way...or is this person special because nothing much exciting has happened to them at all?
- Dialogue. This person might speak a certain way, depending on where they're from. Regional dialects are always important to observe, but a character's upbringing and history may also affect their speech patterns. The daughter of an English professor at Harvard, for example, is more inclined to speak quite properly -- or perhaps she rejects her parent's constant lessons in grammar and uses the worst possible slang instead. Louisa May Alcott made Amy, a supporting character in Little Women, stand out for the way she used dialogue. When it's done well, dialogue is a powerful tool for certain characters.
- Body language. Remember the "close talker" on Seinfeld? Some characters might have certain mannerisms, or use specific gestures when they speak. This makes the character much richer, and easier for your readers to envision.
- Flaws. Nobody's perfect. Does this character have any addictions, bad habits, major hang-ups? If readers spend a significant amount of time with any character, they should definitely pick up on some character flaws. Flawless characters aren't believable, and they just make everybody feel bad.
- Motivations. What's this character's role? It's too easy to think about what drives the main character, and make all their actions clear, while forgetting that the supporting cast need some humanity, too. They're just there to play off your main character it's true, but you have to think about your characters as though they are real people. Real people never see themselves as a supporting character in someone else's movie, do they? Your characters should all have their own ambitions, goals and desires -- something driving them that's not necessarily wrapped up in whatever the main character is doing.
The well-crafted character is one who's fully realized in the pages of the novel, someone with a past and ideas about their own future, someone with current goals and former baggage. Make the supporting cast as interesting as the main character, and you'll make your writing even better.