Keeping notes for your story is important. A list of the characters that appear, and how they are related to the protagonist and antagonist will help keep you from getting confused as the story progresses. If you have a lot of minor characters, these notes are important. The information in these notes can contain a few important details, or you can write up a complete dossier for each one. Remember, keep the back story of the characters to a minimum in your story. If something doesn’t relate to the plot or why a character acts a certain way in a certain situation, don’t add it to the story.
via Writing Tip — 63