To get started, think back to when you were assigned to write a biography for English or history class. In order to do a good job and to tell that person's story, you needed to learn something about him or her. And, to really WOW your reader, it helped if you took some time to discover the good and the bad of your subject's life. Then you knew you could write from knowledge and write with authenticity and authority.
Writing fiction is different...and more fun. There's little to no research required. You have the privilege of inventing your characters and all their idiosyncrasies. In order to do so, develop a blueprint of what you want to know in order to build your fictional characters from the ground up.
I have a questionnaire I developed and use when I build a character. The questionnaire is too big to publish here, but it'll be in my upcoming book, Before You Write. When developing characters, I look into the following areas:
1. Resume. Write a resume about each character. In it include all the information you would put in a resume you might write when applying for a job. It should be a detailed sketch of the person's educational and work history and accomplishments. It provides the structure for your character sketch.
2. Physical Description. You may or may not ever describe your character to your readers, but it's important for you to be able to visualize each character in vivid detail. Some of the things to cover are height, weight, body type, hair versus no hair, hair color, eye color, etc. Those are the basics. It's important to write them down and keep them straight. You don't want to call your character a blond if she's a brunette.
Beyond this basic physical description, you'll want to get a clear picture of physical characteristics that set your character apart, such as walking with a limp, stubby fingernails from chronic nail-biting, the fact your character always wears a baseball cap because he is self-conscious about his bald head, the pendant your character wears always, etc.
3. Quirks. We started addressing quirks a bit in the previous section. The more detail you have in mind about quirks of your characters, the more real they will become. But don't go overboard -- too many quirks and your characters will turn into caricatures. A great example of a character with just the right amount of quirks is the way Jack Nicholson played his character in As Good as it Gets." He became Melvin Udall, that obsessive-compulsive character, and played his quirks with the exact amount of consistency needed. Not all characters need to be that quirky... subtle is often better.
4. Likes/Dislikes. Make a list of your character's likes and dislikes. What makes your character happy and what makes him sad or angry or embarrassed, etc. This list will help you know instinctively how your character will react to circumstances that arise in your novel. Also, list any allergies, chronic conditions, etc., your character might have.
5. Hobbies/Talents. Make a list of the talents your characters bring to the table. If your reader knows that your character works out or was a runner in high school, the reader will expect him/her to do well in a chase on foot. If your character is a good cook, it may add to your story that people drop in on her just to get a taste of her latest cookies. This may not add an integral point to your story, but it'll help to round out your character.
6. Shortcomings. What are your characters weaknesses? Often the weaknesses will make the story more interesting. You don't want characters who don't have any faults. That's too boring. Maybe your character never manifests the weakness during the story, but if your reader knows about it, you've added a potential problem to add a bit of tension to your story. It's always good to give the audience a reason to bite their nails during the book.
That's part one of character development. Get busy on your characters and in the next session we'll begin to weave your character sketches into a backstory.