I think one of my favorite parts of writing is character development. Before I start writing anything, I have a clear picture of my characters in my mind and a decent idea of where they are headed throughout the story.
What always ends up happening is that they surprise me! Through the dialogue and their actions...they almost write their own story. It's as if they really have their own personality and no matter what I have in store for them, they'll take it on in their own way. More than a few times, I try to make a character do something, and I can't make it happen. I can write it a million different ways, but it never fits because the characters have a say.
A good example is from my short story "The Death Bump". The main character, Justin, was meant to just be a regular kid with amplified problems...problems that were heavy enough to make him want to end his life. He's also a kid that couldn't stand his family, including his sister...at least that's how I originally planned it. His little sister Rosie wasn't supposed to play an important role in changing his mindset within the story. But somehow his love for her forced its way into the plot and drove his actions accordingly. I didn't initially write the story that way, but once I gave into it...everything fit and fell into place like it couldn't nor shouldn't be written any other way.
The same type of thing is happening time and time again in my novel, and it adds to the excitement of writing it. Though I know the story's final destination, my characters are telling me how I'm to get there. Neat stuff!