As writers prepare for NaNoWriMo (just a few weeks away!), writing time is spent preparing to write a novel. Since you can't actually start writing until November 1st, all you can do right now is organization/pre-writing. Hopefully, you already have a story idea, and maybe even an outline (or a rough idea of your plot, at least). But there is more to pre-writing than knowing your story.
Just as you need to know where your story is going, you need to know who's in your story. That's why lots of people take some of their writing prep time to create character biographies.
The idea behind a character biography is to develop your character before you start writing. That way, you know your character much better, and can write your characters better, making them more believable to read.
So what goes in to a character biography?
Obviously, the basic character information should be included. The character's name, age, spirituality, ethnicity, etc. This is the kind of information that would go on a census. Beyond that, though, think about who your character really is. What are his/her hobbies? What is s/he passionate about? What is his/her biggest pet peeve?
And once you've thought of all of those types of things, go further. What is his/her favorite book? If s/he was stuck on a desert island, what five things would go, too? If your character were a coffee house table, who would s/he want to sit at him/her, and why?
It's strange, but these are the kinds of things you should think about when creating your characters. After all, if you don't think of them as three-dimensional, how can you expect your readers to do the same? So when you write your character biographies, don't just write the bare bones of a biography. Come up with every possible detail you can. Answer the strangest questions you can think of that would help you (and your readers) get to know your characters.
Something that may be helpful is to get one of those fill-in-the-blank books about yourself. The types of prompts and questions that are in these books can help create great biographies for your characters.
One of the biggest things to remember is that you shouldn't sell your characters short. If you don't know them, your readers won't, either.