There’s some wonderful coverage of the Oslo Murakami Festival here: Murakami Blues.
Haruki himself attended, and spoke about various things including how he forms his stories & characters:
“I have no plan. That is a main thing. When the story ends, I just know it ends, so I stop the story. The characters just pop up in my mind, from the blue. When the Sheep Man appeared, I was shocked.” Haruki Murakami, Oslo 8/23/10