I have a list of names I have create in a notebook (somewhere in my house) and a few brief notes as to who this person is. These notes are not set in stone, they are however a tiny guideline as to what this person could be. For instance, a man named Gualt is a brick layer, uneducated, and has a small family. That is all the notes I have on him (btw this guys was made up from the top of my head.)
Now, here is where I can do one of several things. I can put Gualt in a story that I am currently working on, build a story around him, or change the details. Since I have left many details out of my brief description, it is much easier to fit him in a story than it is to change the character. For this example I will choose to build a story around him.
Once I decide how I am going to approach this character, then more details come rushing in. Gualt is a broad shouldered, darkly tanned man with large calloused hands. He is deeply religious and attends religious services regularly. He has a wife and two children and they live in a small house in town along with his aged mother. His wife works as a maid to one of the high-born who lives in the town, while his mother takes care of the children.
Gualt has his faults: he is quick to anger and has gotten into trouble in the past. He likes his drink strong and is not afraid of a fight. He is often lucky at games of chance which has raised suspicions of him at times. Gualt can barely spell his name but he has an aptitude for numbers. He views strangers with deep suspicion.
Right now, I have about a dozen more details to put in, and twenty different plots I could try out on my poor hapless character. I find as I narrow down the character details I narrow down the story line. Tomorrow I will look more into his setting, so stay tuned!