I’ll keep saying it because I believe it’s important: characters are the backbone of your story. If readers care about your characters (or vehemently dislike them), they will care about your story. Why do people return to soap operas week after week? Because they want to see what will happen when one character destroys another, or discovers another character’s secret, or sleeps with another character’s boyfriend. You don’t have to write stories that are as tawdry as those you would find in a soap opera, but you should have compelling characters moving through your plot. One of the important components of creating a compelling character is crafting a history for them.
For this post, we return to the wisdom of my favorite internet dude — Chuck Wendig. In his post, “25 Things a Great Character Needs,” Chuck talks about the need for a character history. He says, “Your character didn’t just come karate-punching her way out of some storytelling womb. She wasn’t born pale and featureless like a grub only to grow her wings and limbs halfway through the tale. The character’s been around. Whether she’s 17 or 70, she has history. She has life. Stories. Things that happened to her and things that she did…What we see of a character in a story is just the tippy-top of the iceberg, just a nipple poking out of the water while the rest of the body remains submerged.”
This is so, so central to what makes a good character and I think Chuck has articulated it really well here. Just as you’re introducing readers to a world or to a storyline, you’re introducing them to your characters. What you choose to show them as your story begins should not be the only information you have on those characters. Say you begin by telling readers about the job your main character currently has and that he or she is married right now. That’s fine if that’s all you want to reveal to begin with, but you should know the character’s past jobs, past loves, and just about anything you can invent for them. Having all of that background knowledge allows you write a richer, more complex character who has believable motivations. Those richer, more complex characters will help readers engage more fully with and be more interested in your story.
There are plenty of character profile sheets out there on the internet. But I don’t think those sheets are always necessary. If they help you, then go for it! They can be a great guideline if you’re not sure where to begin when constructing your character. But I think writing a rambling, stream of consciousness description of your character can work just as well. Try opening a new document and just beginning to type anything that comes to mind about your character. If you want, make it more structured and write a mini biography of your character, explaining their past and fleshing out their life. Make the character as real as you can by filling in minute, specific details. You can call up those details later when you need to justify a character’s action or explain their feelings.
Once you feel like you really know this person, so that you could predict how he or she would react in certain situations, you’ve got the character history nailed down. Then you can confidently write your story and know that if a reader were to ask you a question about this character, you would have a realistic answer for them. Happy writing!
— Jet Fuel Blog Editor, Mary Egan
JFR Blog 
I agree. The few times I have discarded a book before finishing it have been because I lost interest in a main character. On the other hand, I have read to the bitter end a few “really not worth it” books because of a character who could have been a star with a different story line.