My character creation is simplified a little bit, as I do look at each individual character as a person in my life. I mean, it's much easier to develop the imposing sense of a half-dragon/elf when you feel he's sitting next to you, looking over your shoulder.
The more real your characters are to you, the more real they'll be to your readers. For instance, in Everyone Dies At The End, I struggled at first to find a voice and flow for Earl because I tried to approach him as a voodoo doll that I could torture. But as the story evolved, I watched the basic outline of a character take on a life of his own.
That's the other thing, give your characters room to grow. Yes, I know you need to restrict their growth for certain parts of the story. But if you stifle your character in rigid sets of rules that they can't break, then I believe you're also stifling their ability to grow and be unpredictable. (If there's one thing we humans are, it's unpredictable.)
Now, I'm not saying don't have a plan. I don't mean to imply that my characters are chock full of chaotic traits were I just throw things in wily nily as I see fit. Have a plan, have an idea where you want them to go, but don't grow so attached to that ideal that you lose your ability to be flexible.
One of my favorite quotes all time was said by Bruce Lee. He said, "You must be shapeless, formless, like water. When you pour water in a cup, it becomes the cup. When you pour water in a bottle, it becomes the bottle. When you pour water in a teapot, it becomes the teapot. Water can drip and it can crash. Become like water my friend.” And that leads to my last bit of advice.
BE your character. I know, it sounds funky, clunky, and full of holes. How can you be someone other than you? But from many extensive years playing RPGs (Thank you Dungeons and Dragons) and sticking myself in others people shoes, I can tell you it's easier than you think.
Make the choice to be a smart ass for a week if your character is going to be that way.
Make the choice to look at the world around you with cynical eyes if you're character is going to be that way.
Hell, if you're book is nothing but sparkling rainbows and butterflies, then picture yourself as the unicorn walking through that wonderous land and spreading the love.
In conclusion, character development is just like personal development in my mind.
Riley is an ex-CNA who found himself unable to do the job he loved. Injured, out of work, and stumbling through life, he happened to start writing down his thoughts. Once that happened, he fell in love and has been writing since.
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