WHAT YOU DON'T NEED TO KNOW ABOUT YOUR CHARACTERS

1. You really don't need to know every last detail before you start writing.  A lot of the joy in writing is finding things out yourself as you write for one thing.  And the purpose of the first draft is just to get your story down in its barest form.  You know it will need work.  It is at the first edit you can work out yes, I need to know this about that character or I need to put more in here because...  and there must always be a really good because to justify what you add in.
   
2. Unless physical description is phenomenally important to your story and how your character behaves, I think it is the least important thing to know about straight away.  What the character is like in terms of traits and attitudes is far more important than knowing they were tall, dark and handsome etc.
   
3. Unless writing a political story, do you really need to bring in your character's political affiliations?
   
4. Anything that gets in the way of your story.  Each and every detail must be vital to your plot and the accurate portrayal of your characters. There must be no feeling of irrevelancy.
   
5. Your character's family tree unless relevant to the story and even then you will almost certainly  need to drip feed in the information rather than share the information as a block.