I've Got Soul But I'm Not A Soldier...

I'm curious to learn how people write. How many people map out their entire novel prior to writing? Do you know the ending first and write based on it? Do you begin in the middle? Or do you just write?

I just write. My book runs like a movie in my head. It's so wonderful and fulfilling--to know that such a place exists in my mind. It's very cool to have others read my book and share their perceptions of my characters and places. It's especially interesting to see how people view them from my descriptions and if they are anything like what I've written. From my reading experiences, I know that I have simply ignored description of a character because he's already come to life in my head (for instance, while reading Twilight, I pictured Edward with blonde hair and favoring Kenneth Branagh--He played Hamlet in the 1996 version).
Here's a picture:

Too funny, huh? This could be because I was in High School at the time and watching Hamlet in class after reading it. However, it's still interesting!

Anyways. I always find the writing process really interesting because so many people do it differently. For me, my characters play a HUGE role, and I just done mean simply by being, they tell me what they want to do. I cannot control them, believe me, I tried! It's too exhausting. After these 8 years of writing, I have realized that they have their own life. They are busy living, experiencing tragedy, falling in love, going on adventures! They do things I don't like, and they make me cry. It's usually at this point where I want to change what they've done...but the story doesn't work that way...and I know that they're right. So I listen to them, no matter how sad or how much I cry.

What do you guys think? How much control do you have over your characters? Or do they control you?