Writing backstory is a delicate balance. Write too much and your readers will get bored waiting for the plot to move forward. Don’t write enough and you’ll leave readers hopelessly confused. A masterful writer will know how to weave just enough backstory into their plot without overloading readers.
What is Backstory?
Backstory is the history of the characters and places within your story. It can be given through flashback-scenes or reflections by the narrator. It's an essential element to character development and world-building because it provides necessary information about what happened prior to the action of the story. Every piece of writing includes at least some backstory, but the trick of crafting a story that is both coherent and engaging lies in the question of how much to use.
A good rule of thumb is to never use more backstory than you absolutely have to and never use it until you absolutely have to. In a situation where a character makes a decision heavily influenced by something that happened to them before the narrative began, you don’t want to leave your readers high and dry as to why that character is suddenly acting in such a way. However, you also don’t want to begin your story with a detailed timeline of that character’s life leading up to the action of the story. Similarly, if you are setting your story in a world that you have created, you don’t want to hit readers with a forty-page history lesson up front. Giving large chunks of backstory at once slows the pacing of the story and takes readers out of the immediate action of the main plot, and it can be tedious to read. Furthermore, good writing will eliminate the need for a lot of backstory because readers will pick up on rules and customs that the characters abide by as well as the personalities of the characters simply by reading the present action.
You can judge whether you have used an appropriate amount of backstory by reading your piece as if you knew nothing about the places and characters beforehand. Based solely on the words on the page, do you understand enough about the situation to continue reading, or are you lost? Does the story drag on? Is all the information given really necessary? When in doubt, cut out the detail in question. Read it again. Does the story still make sense?
Writing backstory is one place where the old maxim “less is more” may actually apply. Still, it is important to make sure readers are provided with sufficient background information. The amount they need depends heavily on the story, so it is ultimately up to the writer to determine which information is necessary. It is also important to note that you, as the author, need to know more about your characters and world than you explicitly write in the story. Having the background information in mind will allow you to subtly add detail to the story without interrupting the action. But keep in mind that just because you know every battle in every war in the history of the world you created or every story of every tooth that your main character lost does not mean that your reader needs that same information.