I have a real issue with character development when I first start writing a new story. I get so excited about my new idea that I tend to dive into writing without getting to know any if the main players very well beforehand. This always results in the story fizzling out very quickly, ending up in the scrap heap. It's only when I spend time with the characters first that they then take the time to tell me their whole story.
So what do I do to get to know each character?
Step 1. First I like to work out what event from their past has set them on their current path, whether they know it or not. I write scenes from their perspective (even if they are never the perspective character in the story). It might be a scene at school where their teacher is a total monster to them, a scene where they experience rejection from a love interest, a scene where they receive positive feedback from something they have done. All of these things shape who we are as people, and they will shape your characters as well.
Step 2. The next thing I do is work out my character's religious/moral beliefs. What a person believes on colours the way they view the world. Very, very religious people tend to wear blinkers when placed in situations that go against their faith, as do hardcore atheists. Not everyone is flexible in the face of new evidence.
Step 3. The final step is to work out what motivates each character. Often this is a combination of the first two points. Experienced a childhood of neglect? You might be motivated by positive affirmations of others. Have unbreakable faith in your god/s? You might be brave in the face of bodily danger. Grow up with a parent with alcoholism? You may have a zero tolerance attitude to alcohol/a close bond with the bottle/an addictive personality that sees you constantly seeking your next high.
Once I know all of this about my characters I spend a lot of time talking with them, often out loud or in my head while I'm out walking or driving. I throw them into imaginery situations and see how they react. Then, of course, I write my story and reassess each character. If they have not behaved as I had expected I go back to work getting to know them even better to work out why.
It's no wonder I cry so hard when I have to kill my darlings.
So tell me: what do you do to develop three dimensional, consistent characters? I'm always looking for new techniques to try.