Bring on your torture, your bullets, your pains
I would recommend you start with a plot line. I make pretty flow charts. It relieves stress from writer's block later down the road. Next, decide if you're going to write in first, third, or third person omniscient point of view. Then start typing or writing somewhere. Normally the best place to start is at, well, the beginning of everything. Focus on one or two characters to begin with, and develop them. From there, let your words fly.
And in my heart, things aren't the same.