Imaginary Friends

[Disclaimer: I have never been diagnosed with any sort of mental illness. The methods described below are simply an exercise of the imagination]

If you're anything like me, (and I expect you might be) you probably had an active imagination as a child, and may have had an imaginary friend to have various adventures with. As we grow older, we begin to realize that imagination and reality are separate things, and we let these imaginary characters fade back into our heads. But, there's a secret that most people don't know about: writers never really cut all ties with their imaginary friends. They may not be the same as the ones from childhood, but writers are constantly talking to voices in their heads, and continue to have adventures with them, in the form of stories. And if you're lucky, people will pay you to do it.

Talking to your characters is kind of a strange process. Not to make light of mental illness, but I think the best way to describe it is like a self-imposed form of schizophrenia. While you remain fully aware that these are imaginary people you're interacting with, at the same time, you allow them to act and say what they want to. This method is not for everyone, but I think it really is one of the best ways to figure out characters.
For those of you still with me, let me describe how I discovered this technique to give you an idea of the mechanics of it:
This happened to me on a walk home from work some years ago. My mind was wandering, as it does when I'm walking anywhere, and I visualized a character walking beside me. He was a well groomed man of indeterminate age, wearing a well made black suit, regarding me with a mixture of curiosity and disdain.
"You realize you're a failure, don't you?" He said to me.
In retrospect, this was the moment that I realized that this actually worked. If it had merely been a daydream, I certainly wouldn't allow a character to show such insolence. Allowing characters to speak for themselves rather than making them say what you want them to is key in this exercise.
I, of course argued against his observation (in my head and not out loud, of course), even though I had not been published at that point.
The character (I call him Mr. Black, although I suspect he may never tell me his true name) went on to outline all of the things I had failed to do in my writing, and steps that had not yet been taken. At this point, I was starting to get angry. Much to my surprise, another of my characters burst in and started arguing with Mr. Black on my behalf. In the end, he ended up talking Mr. Black down, although he did not concede his original point as he walked off into the distance.
It was an almost magical thing to witness in my imagination, and something I urge those of you with strong imaginations to try for yourself. There are all sorts of things you can learn from simply talking to your characters. If you're stuck with a story, let them come to you and ask them what they would do. Their answers might surprise you, but if you've figured out who your characters are, they will give you the right answers every time.
If you've done this, or try it because of what you've read here, I'd love to hear your experiences with this method!