I liken this to hosting a dinner party. Long before I plan the menu or select the vino, I think about who to invite. Which guests will mix well with the others? What common bonds might they share? I may think to myself that I surely have to invite Tyler - he's always good for jokes and injecting humour into an evening. And of course, I have to invite Jim - he always has wild stories to tell. Julie just got back from a trip to Brazil and I can't wait to hear about the trip. Donna will probably bring her guitar and after dinner drinks may turn into a sing-along. And I know that if I invite both Liz and Andrew, there will likely be a heated debate about politics or current events since they are polar opposites.
You get the idea.
Once I know who I'm dealing with, the plot slowly starts to come together. If I know Andrew is a bit of a hothead, then it will be easy for me to thrust him into situations and know just how he will react. And when it comes to dialogue and Tyler - piece of cake because I know he will crack wise at any opportunity.
There are all sorts of charts and lists that one can create (or find online) to help you with character development, but I don't use any of those. I'm fairly loose about backgrounds - what I do for one I may not do for another. But generally, for most of my main characters, I'll figure out:
- political leanings - and do they usually vote?
- zodiac sign
- education (major), or did they drop out of high school?
- religion - whatever it may be - do they practice it actively?
- where they fit in the family tree (middle child, youngest, etc.)
- relationship with parents (and were they divorced?)
- ethnic/cultural background
- attitude towards some "hot button" issues, like marijuana, immigration, gay marriage, etc.
- talents/hobbies that have nothing to do with the plot or with their jobs (do they play an instrument or are they on a sports team?)
The list could go on and on (do they prefer Coke over Pepsi, Apple or Windows, are they afraid of heights, do they have/do they like pets, do they have any allergies, etc.) but the above points usually give me an idea of who my character is. And that's a great start!