I made a joke on Twitter last night:
"I wish I could write a thoughtful piece about including pages of exposition without ruining pacing but I obviously know nothing about that"
Well, perhaps I'm a little bit wrong. I know a whole lot about including exposition in ways that impede and foil pacing, so naturally I guess I know a bit about what NOT to do. I might as well write about that now.
The two dangerous ways to deliver exposition are through paragraphs of unapologetic backstory or question and answer sessions. There is a time and a place for both and a time and a place for neither. I shall explain.
I open my story with a Question and Answer session between a six year old boy and his grandfather about the nature and rules of my universe. These are the things that everyone reading my book needs to know in order to understand where they are and what the heck's going on. Paragraphs of exposition when you have nothing invested are boring (that is unless it's really exciting exposition) so I introduced two characters to feed off each other with a bit of an underlying b story to keep the audience interested enough to read on. I am well aware this segment is not perfect. I've re-written it a ton of times, every pass making it shorter and more concise. These are what I have come to call "Bamboo Trap Scenes"- pages and pages of characters sitting and talking about stuff they already know.
Your standard bamboo trap is usually set up in jungles or forests consisting of a deep pit covered loosely with sticks and leaves. The trap is sprung when an innocent passerby steps on the cover and falls down to be impaled on several pointed bamboo sticks stuck in the bottom of the pit. This is about the same unfair painful feeling you get from a QnA scene gone wrong. You wander in innocent enough but before you know it you're waist deep in pages of information, trapped and helpless. A good sign that this has happened is when your characters start getting bored. When their whole contribution to the conversation is "What about this?" "Tell me about that" "Why is that". When the engineer in your story-locomotive is sitting around doing nothing useful, the audience riding the train is doing the same. No matter how interesting the backstory is, Bamboo Traps are not a fun place to be stuck in and should be avoided at all cost.
The other option is blatant blocks of exposition. I consider this a more honest approach; we've got a ton of exposition, why force the characters to sit around and discuss it for three pages when the prose can lay it out plainly for one? The downside is that now your characters aren't involved at all! I call these bits "Lectures" because it's the author abandoning anything the characters were previously doing while the audience takes a minute to do some supplemental reading that has nothing or little to do with the current plot. This throws a huge wrench into pacing and should only be used at times where a little separation from the action doesn't matter - like at the beginning of a chapter, after a scene break, or in closing. I still try to keep these things brief. If the characters are off-screen for more than a page I go back and start eliminating things to shorten it up. This has worked in my favor before - bits of exposition I've had to cut out of one Lecture sometimes surface later on in dialog or as flavor text. This leads me to perhaps the wisest and best form of exposition; the gradual kind.
The best way to learn about a world is to explore it, go places and learn about them as your characters see them; talk to locals to learn bits about what happened in the past and the present, make events take place at historically significant sites so that your backstory is told parallel to your main one. This is a good way to make your world feel established, because people only stop every few feet to read about the past when they go to museums not when they're on adventures. Bundle events with backstory as much as you can to slip the bits people need to know naturally into the story as they experience it. The first example of this I can think of was pointed out to me by a scriptwriting friend several years ago when we were having this discussion.
In National Treasure starring Nick Cage, the history of a certain document and how it got into his fathers hands is explained as a diversionary tactic. Nick is pressing his dad for specific info and to avoid answering, his father distracts the other characters with a story about the document they are studying. It was obviously exposition, but it also served a purpose and was more than one scientist walking up to another scientist and saying "Boy I'm glad Dr. Klien put us both on this project together. I get to study how rats reproduce, you get to test your new rocket fuel and the pay's good too!" The scientist conversation would not happen in real life, but the National Treasure one conceivably would. This is good implementation of exposition.
Of course there are exceptions to every rule. I hit a point in Act 2 where a huge element of the past was suddenly revealed. It was not the kind of discovery that could be stretched out amid worldbuilding scenes and was important for setting up decisions and motivations for the next few chapters. Cat found herself sitting in not one but TWO one-on-one question and answer sessions. I fall in to way too many Bamboo Traps for my own good, so I had to find creative ways to get the information out without making Cat a "Then What", and employing Lectures wouldn't do for the timing.
My answers were to turn the Traps into something else. The first became a game; the character we were receiving information from was actually interesting to talk to and spoke in slant for most of his replies. This gve the audience something to ponder as the exchange progressed as both they and Cat try to figure out what exactly he's talking about. In the second I decided to tell the history as a tale within a tale delivered by a storyteller complete with dialog of the past characters. I'm content with this because it physically removes us from the Trap for a good chunk of time, making the time we do spend speared in the pit more manageable. If nothing else it connects the backstory events to real human emotions the readers can relate to soy they'll be distracted enough to forget that we're two people in a room asking questions back an forth.
These are all points to consider when writing your exposition but I'd like to reiterate that I write Bamboo Traps and Lectures constantly in my first drafts and it's only in the revising process that I solve and sort them out. I'm sure I'll talk about how I mold and handle drafts later because Lord strike me down if I try and stop talking about writing this book, but first drafts are just for putting your ideas on paper - letting them out of your head to make room for more. Once they're on paper you can see them in daylight and figure out the parts that need work. Write first off the cuff, if you worry too much about nitpicks like Bamboo Traps, repetitions or the passive voice you'll overwhelm yourself. That said I'll complain about reps and pvs in another post.