Let’s say you are working on a novel. You decide to make it a crime novel. When writing any manuscript for a proposed novel, an important element of the story is the main character. Just like in a movie script or a Broadway play, it is important to provide a background story for your chief protagonist. You can start with a name for the character. When picking out a name this can give you the opportunity to expand a full story around it. Was he or she named after a relative, or a favorite person from history? From there you may consider where your character comes from. Now you can start to flesh the character out. For example, suppose you decide your main character for the crime novel will be a private detective. For the purpose of this example, let us make the detective a male, about 40 years old, with a sordid past. His name is Jacob Nomad. Jacob has a biblical connotation, doesn’t it? Perhaps that helps to shape him for a life of solving crimes.

Now you ask yourself, how did Jacob become a private detective? Maybe the character was previously employed by a big city police force. Let’s make him a former police captain. That leads to the question, what happened in the past that cost Jacob the captain’s job? Maybe he did something wrong. Marital problems at home? Or a drinking problem, which led to poor job performance? Or, you decide it was police corruption and Jacob was forced out by the real crooks in the force.
  

Your character now has a sordid past to try to overcome. Perhaps this caused the poor soul to drift from town to town over the course of a few years trying various jobs to feed a drinking habit. To try to better himself, Jacob decided to join the army and he winds up fighting in a war. After that, your character deals with the effects of combat. Post traumatic stress disorder causes him to have nightmares at times. Despite all this, Jacob decides to start over as a private detective.

You have just fleshed out your main character. With a  flawed but very interesting background story you have a main character and you can use it to show his motivation for being a detective. After all, he was once a police captain so you know he has the skills to be a good private eye. Many possibilities abound to add to the story. A person from his past may be a client which leads to a return to the big city to confront those in the police force who may have cost Jacob Nomad his former job. He can have flashbacks to the time he was a bright police cadet and the cases that led to promotions until he became a captain. With this information you can work out your story, knowing you have a flawed, but relatable hero to root for and an added dimension to your novel.