Every person, every character, has a past. They have events and circumstances that made them into the person they are today. This history is known as the back story.
When developing characters for your novel, you need to know at least some of their back story. For main characters, you need to know their history extremely well. You should know them inside and out.
Creating this back story can be a time-consuming task but is a necessary part of building solid characters that come to life for the readers. (And back story just doesn’t apply to people. Towns, schools, worlds – all have a back story.)
So now that you know all this detailed information, how do you go about letting your reader know about it? Or do they need to know it?
The basic rule of thumb is to tell the reader only what he or she needs to know to understand what is happening in the story at that moment.
Basically, you want to add the back story in little bits – a couple of sentences here and there. You don’t want large blocks of text. This stops the momentum of the story. Writing back story stagnates your story. It is telling the reader information rather than showing them. It doesn’t engage any of the reader’s senses. They are no longer actively participating in the story. They are busy reading background that might or might not be relevant to the action that is about to start.
I read on another website a good way to think about this. Consider adding back story in terms of taking bites. You can’t eat a whole cake in one bite. However, you can eat it by taking lots of little bites. Trying to eat a cake in one bite could cause you to choke. It is the same with back story; include it in small bits so the reader doesn’t choke.
Because back story slows down the reader, one place you want to make sure you DO NOT include a lot of back story is in the beginning of your story. You only have a few pages to hook the reader so use those pages to give them action. Yes, your character might be motivated by their past, but the opening pages isn’t the place to go into depth about that past.
The best fiction is all about action. Your job is to portray the action and let the reader draw his own conclusion. And it is easier to do this with well-developed characters whose actions are consistent with the back stories. Just remember to not slow down the action telling the reader that back story.