I like the idea of writing mini biographies or character sketches more than lists filled with mostly irrelevant information. ninja Past experiences, motivations, things that can affect their actions throughout the course of the story...
Usually I just write, though, and "discover" the character as I go. Generally I at least have a vague notion, or a sketch I've drawn that can help give me ideas with notes jotted on the side. (Y'know, things like approximate age, where they're from, that they hate snakes, et cetera.)
In short stories, at least, it doesn't matter if a character loves pistachio ice cream and is the youngest of six siblings if the story's about solving a murder, and ice cream and that they were the baby of the family have nothing to do with anything.
Unless there's a scene involving an ice cream shop and a meeting between the character and one of the older sisters who still dotes on him.