I know a little something about having a troubled and troubling past. And present. So do most people I know.
As a writer, you're going to populate whole fictional worlds with people with complicated pasts, or, at least, back stories. And as a writer, you're going to need to figure out how to let your readers in on that back story (or enough of it) without boring or overwhelming them. Here's my back story presented in convenient meme form
Informative and concise, right? But you can't place a useful little meme into your novel, so here are a few humble suggestions on what not to do:
Do not start at the beginning of your character's story. "Chapter One: I am born" worked for Charles Dickens in David Copperfield but he wrote in a different time for a different audience and, as Stark just pointed out to me, legend has it he was paid by the word. If you want to let your readers know a character's entire life story, it's still better, usually, to not start at the moment of their birth. Even if there is something odd or important about it, you can tell it later, when it becomes important to understanding the character and the story. You can do this through a natural conversation or a flashback of sorts, but be careful of those flashbacks. Too many and you'll give your reader vertigo.
Sometimes it's useful to think of the relationship between you and your reader(s) as a kind of friendship. You probably don't know everything your best friend did from the moment their lungs first took in oxygen and if they had tried to share these details with you early on in your friendship, you probably wouldn't be friends now. TMI. A relationship has to develop over time. That's why as a writer you want to avoid the information dump. While it seems efficient, perhaps, to front load all of a character's relevant data early on so you can get on with the story, that robs your reader of the pleasure of discovering the depths of your character over time and it gets in the way of the relationship you want to form with your reader, which needs, like all relationships, to develop gradually.
When I first met Tony Stark, for example, he pissed me off with a barrage of questions about my past, my condition, my feelings, why I turn into a green rage monster. He even poked me in an attempt to get me to spill (or bring out the other guy).
Okay. You want to avoid the information dump. But how do you know when and how to weave all that back story into the narrative? I wish there were a magic formula for that, but if such a thing exists I haven't found it. I know that it annoys me when people cryptically refer to their pasts. Natasha and Hawkeye refer, now and then, to "that time in Budapest" and I have no idea what they're talking about. It seems it was a charged time for them and something they don't want to explain to others. That's their choice. But as a writer you have to be careful about throwing out hints about a backstory that go undeveloped or you risk making the reader feel like they are outsiders to an "in" joke.
You also don't want to throw in a bit of back story just to "pad" your story. A character's past behavior is meant to explain present behavior, not to make your work into an epic-length tome. Loki is a megalomaniacal jackass who wants to rule the universe because he didn't get enough love from his father. Why he feels this entitles him to rule the universe is best left to a psychologist to explain but it helps me to understand him and his motives. His past self helped to form his present, as mine did. My past self was afraid of what anger would reduce my father to, especially in regard to how he treated my mother; my present self is afraid of what my anger will reduce me to (or how it might reduce a major city to rubble). But if I were a character in a book or movie, you wouldn't have to know all of the details of my childhood, all of the traumas that make me the poor candidate for a season on The Bachelor that I am today. A good writer can deploy one economical detail to tell a whole (back)story:
Sometimes one detail, one short line, can reveal more than an entire case history of a character could.
So even if you have a whole notebook full of back story for each character you've written, lists of their favorite foods and songs and what color shirt they wore to their first day of third grade and how that day went, don't throw it all in the book. Think instead of a few key details, a few representative moments, that will reveal all of that and leave your reader wanting more.
The Hulk reminds me that there's an awful lot of power in what you don't say sometimes. Take it from a guy who can frequently be reduced to monosyllables. Or grunts.
Until next month - Bruce Banner and the Hulk out.
* the fake film poster above comes from a Clint/Natasha fan fic Tumblr, http://fuckyeahclintnatasha.tumblr.com/post/22620826676/well-always-have-budapest