I have little taste for writing low-concept stories. The mantra "let the story write itself" smells like BS to me -- maybe it works for some purposes, but not for mine. Same with "it's not about what you write, but how you write it." I do not write for the sake of writing, nor to make money. The only reason I write is to get an idea out of my mind and into words so that I can play with it and so that other people can absorb the idea in an enjoyable way. The idea consists of an interesting situation that leads to events that unfold and conclude in some shocking, heartbreaking, or ironic way that gets the reader to think about human nature from an unconventional perspective. Characters are not my children. I do not write to give them life or to watch them grow. I have an idea, then I decide to turn the idea into a book, then I design characters as tools for developing the idea. So I first come up with a big picture plot. I focus primarily on designing the ending for maximum emotional impact and intellectual appeal. I focus secondarily on designing plot threads that lead up to the ending in a way that makes sense. There are also subplots with their own conclusions and their own emotional and intellectual impacts, and I decide how to fit those into the big picture. Then I design characters who would believably perform the actions required to drive the plot. Once everything is believable, I go overboard on character design. I decide on their personality types, communication styles, personal background, hobbies, interests, careers, opinions, etc. I keep this information in character sheets. The character sheets make extensive references to the plot in order to justify design choices to myself. Those justifications feel like putting the pieces of a puzzle together. Small picture plot details are derived by answering the question "how would these characters act in this situation, with the constraint that their actions fit into the big picture plot?" If I have done my job, then no reader would ever guess that I designed characters to drive the plot.
Pretty much this. Since I don't start writing until I have a pretty good idea of where I want the story to go, I start with generalized characters in their situations then think about what kind of people they need to be and what kind of relationships they should have to make the story happen. The fun part is seeing storyline and characterization come together as one influences the other. My second novel (as if I had the first one finished, yeah) first saw fingers to keyboard in a writing class exercise on "A typical day in your MC's life," and I included an argument she has with her brother over the settlement of their father's will,. This scene ended up in the novel. From that my ideas about the troubled relationship between these two has expanded and grown and led to new plot ideas and provided answers to plot ideas I already had. As to how I plan this all out, oh, gosh. That usually happens in my head when I'm straightening shelves at my boring sales assistant job!
Mines usually come to me instantaneously because of the way that I come up with ideas. All of my stories begin with a scene, an exchange between two or more characters. As I expand from there and more scenes and idea comes to me, the characters that are necessary to make it work usually come into existence along with the scene. This usually includes everything about them except for their name and general appearance. I simply refine from there based on what the story demands.
I usually base characters off people I know, or combine personality traits of people I know. This usually helps me to give them a distinct voice. I usually know their back story as well and what their role is in the narrative. Beyond that, I just throw them in with the rest of the fish and see how they swim.
