I know many writers who have done this in the past, and for me, it never really made any sense. If anything, it kinda bothered me, as I didn't think I could find actors that would fit my characters. But, duh, they are actors - and there is a lot you can do with make up and such. Being a visual person, this was really just a fun exercise. But I must admit that I do not think of these actors as I'm writing. It's still a cool thing to do for kicks.
So my current project is still in revision hell, trying to get it in descent shape before it goes to my publisher's editor. My novel is titled Dragonfly Warrior, and it's the first book in my Mechanica War series. It's an alternative history - steampunk novel that I've been working on for a pretty long time, and it's publication date is slated for the end of July of 2012.
Here are my choices for casting my cinematic version of my WIP:
Matsuda Shota as Zenjiro
This popular Japanese actor is my choice to play the warrior prince of Nihon sent on a quest to the untamed corner of the world. So idealistic, naive, and pretty arrogant.
Richard (Rick) Mora as Enapay
Rick Mora has been in a cool zombie/cowboy movie, and even had a small part in Twilight. He's a great fit to play the airship pilot hotshot that is my foil to Zenjiro's straight-and-narrow character.
Sienna Guillory as Neva
I first noticed this actress in Eragon, and she was the only bright spot in that movie. Then, she got my attention in playing Jill Valentine in Resident Evil. That's awesome, as Neva is a pistoleer hunting down the man who abducted her son.
Ken Watanabe as Kawatoku
Of course, every successful movie needs some star power. So I chose Ken Watanabe to play the part of Zenjiro's father and emperor of Nihon.
Now the bigger question is, would a movie like this even get made? Some would say no, and that I would need to WHITEWASH my casting (i.e. The Last Airbender, Dragonball Z, and Akira.). And I say to hell with Hollywood whitewashing. My novel has Asian characters, and they will have Asian actors play them damnit. No offense to white people, as I love you all. But I could do several posts on whitewashing.