I suppose I should also confess that, in addition to having lifted many of the ideas from my playwrighting and directing classes back in my miscreant Theatre Major days, I recycled some of this from one of my Last Dark Art columns on RPG.net a coupla years back. I figure if you can't cannibalize yourself, there's no point even getting into the biz at all.
Dramatic Plotting Made Simple
...if not, perhaps, "easy" as such.
What follows is a very particular slant on the idea of plot-engineering, designed to (hopefully) jog the writing of those who do character well but couldn't outline with a Maguffin to their head, or who intend to spend their precious October prep time creating a really amazing setting without being bothered to decide ahead of time what happens there. It's founded on the principles of playwrighting as I learned them as a wee dramaturg at the knees of several learned gurus of the Theatre some witch's dozen years ago, though the application is very broad and flexible; thus, Dramatic Plotting, in several senses of the word.
To understand plot, it is necessary to understand the smallest unit of plot: the event.
An event happens when pressure is applied to the characters in sufficient quantity to force one or more of them to take action to relieve it. If this is done right, the resolution creates a new pressure which must be dealt with in turn, and so on until the force of the narrative winds itself down in a satisfactory way.
Constructing an event can be tricky, especially if you have any inclination to resist being cruel to your cast. A general guideline is that the bigger the initial pressure, the more momentum the events that follow from it will have. Pressure is the fuel that drives the engine of plot; don't underfuel your story vehicle. Turn the pressure on early, and crank it high.
(So what makes a good source of pressure? It depends on the people it's happening to. The key is that it doesn't have to be earth-shaking - it just has to shake up the world of the characters. People are very capable of blowing up trivial matters to life-and-death proportions, as long as something they care enough about is in the balance. Know the needs and desires of your characters; find out something they want badly, and take it away from them.)
The other thing that makes event-construction challenging is that it's very tempting to create a good, solid event that resolves too easily and ends the story. Once again, avoiding this requires being mean to your characters. This is where you need to stack the deck: create dilemmas where the only choices are two bad ones. Force them between desires that are mutually exclusive. Set up conflicts that aren't good vs. evil, but good vs. good (or bad vs. bad, even). Make them give up something else they treasure in order to something they want just a little bit more, and then give them a reason to regret it. Do whatever you have to do to keep the pressure not only on, but escalating, so that each new solution has inherent in it a new problem (or two, or three). And remember that, very broadly speaking, happy and contented people make for lousy stories. Give them a reason to be miserable, and watch events unfold.
The advantage of this method of constructing (and thinking about) plot is that, done right, it develops organically, out of the characters' own conflicting motivations; events that are created out of pressure don't feel artificial or contrived, as if the author is simply moving the cast around like pieces on a board. The disadvantage, of course, is that it has the tendency to take on a great deal of runaway momentum, and may not end up having much to do with where the author intended it all to go. This is Okay, of course (and after you do it for a while, you learn to nudge the pressures to put people where you want them to go), but may not be satisfactory to those who like a great deal of structure.
Not the only way to run a novel, obviously, and certainly not the only useful one; but an approach with a great deal of potential for breaking the writer out of the trap of having a lot of cool ideas and nowhere to go with them, and keeping the wheels of what-happens-next turning until you find a way to wind them down.
(Several posters come in with good questions.)
An example of an event? Okay - a well-known one, even. (I'm assuming y'all speak Fannish, or at least have been to the movies in the last few years.)
Frodo finds out his crazy uncle's magic trinket is actually the legendary One Ring - and not only is Sauron trying to get it back, he probably knows where it is and is sending the Black Riders to collect it as we speak. When, and not if, they get to the Shire, they'll tear the place apart until they get what they came for. Pressure abounds! Frodo takes the Ring and hits the road. That's an event.
Of course, that means now he's on the road, in territory he's never been, hunted, and by the way trying to keep his friends and his gardener from getting themselves inadvertently killed for his sake. Lots of new pressure, and that's not even including the fact that Gandalf doesn't show at the planned rendezvous, and now there's some shady guy in a cloak eyeballing him, and the enemy's closing in... and so on and so on all the way to Mount Doom.
Or how about this one, from more literal drama: Lear is King of Britain, but he's getting old and tired. He decides he's going to divide up his kindom among his three daughters and retire to a life of leisure. (This is arguably the first event, and note how it's a small pressure and a relatively minor event - and note too that the action is already in motion when the curtain comes up, and how we're coming in just as things begin to get interesting. This is an Important Lesson.) But just as the ceremony's going well, Lear springs on everyone his wacky idea of asking his daughters how much they love him - in front of the court and all the nobles - and rewarding them in proportion to how much they stroke his regal ego. Pressure in spades! And it turns out that his youngest is caught between her duty and her integrity (or possibly stubbornness) and just will not play along with Dad in his quest for empty flattery; she's caught between two bad choices and makes the only one she can. That's an event. So Lear goes apeshit, declares her banished and by the way disinherited, and generally makes a big ugly scene in front of the gods and everyone. New pressure! So now Lear's right-hand man Kent decides he can't keep his mouth shut or leave well enough alone either, and calls the king out... and so on. You get the idea.
As to how many events are necessary for a decent novel - well, "as many as it takes" is the wiseass answer, but also maybe the best one. You need to start building to an event every time it looks like nothing is in danger of happening. This is the idea behind the "When in doubt, send in two men with guns" advice or its several variants. It means that when things are floundering, it's probably because the pressure's letting up before it needs to. Turn up the pressure! Spin the dials until something breaks!
A better answer, maybe, is: Look through the books you love - the ones that were real page-turners. Find the events - the places where Something Happened that made you say "Oh my god! What's next?" Events, and the new pressures that result from them, are the hook that keeps the reader in the tale. You need as many as necessary to keep the story in motion and the reader hooked.
It occurs to me that I might not have answered the questions of yesterday's responders as fully and well as I should ought to have done; and that Examples from Lit'rature, however well-diagrammed, might not offer much help in how to build your own. So.
How do you create an initial event? Well, you (presumably) have your characters, and you have your setting, and you have an understanding of how the one interacts with the other. Somebody here wants something (and if they don't, you better get in there and make damn sure they do). Whatever initial pressure you introduce has to engage the characters in what they desire.
Desires come in a lot of flavors, but you can do well by the basics: Love. Comfort. Home. Dignity. Honor. Those come up all the time because they're things lots of people can relate to wanting, and wanting badly. (And by the way, lots of other needs boil down, in the end, to one of these.) But the trick is, too, that you need to be specific. What are the boundaries of this person's honor? What are the requirements of home? What sort of love does this person need to find to be truly happy? Once you establish this, you should also pinpoint whether this want is something they're looking for, or something they have that you can take away. This is going to determine the nature of the pressure you exert, and how you're going to really get them where it hurts.
So if you're going with love (and there's no reason why you shouldn't), and you're further exploring your protagonist's need for romantic love, and you know exactly the kind of Honorific Right they're seeking, you've got a nice little hook you can slip into them to begin to apply your pressure. Now you can start throwing obstacles between them and the thing they're after. Boy Meets Girl And They Fall In Love And Are Happy does not make good story. Boy Meets Girl and one of them loves another; or their love is forbidden; or one of them has Other Obligations; or one of them dies - all do. This is why love triangles, Romeo-and-Juliet scenarios, and tragic marriages of one kind or another are such popular and durable ideas. They're cliches because they continue to work.
Now - whatever obstacles are messing up your characters' lives (creating pressure), they have to be present and immediate, or nothing is going to happen: no event. And part of the trick of making it work right is that the characters' desires have to measure up to the pressure at hand. Boy meets girl (or whatever recombination or variant tickles your squid, natch), and one of them loves another, and the other shrugs and moves on: Also not a story. For a proper, solid event, people need to be, in some measure, desperate.
This is where you need to make sure the pressure is at a high enough level. "The love of my life doesn't love me, but I can wait" is probably not sufficient to create an event on its own. "The love of my life is marrying Bruno Brutenheim unless I do something about it TONIGHT" - probably is.
The exact nature of the event depends very much on the nature of the people involved. In the scenario above, what our hapless romantic hero will do to resolve the pressure depends on what kind of guy he is. Does he try and serenade his beloved with her favorite lovesong? Propose to her himself? Seduce her after the rehearsal dinner? Kidnap her? Kill Bruno? The important thing is that he has to take a big acton, and that the action has consequences. Those consequences are the source of your new pressure.
One more thing I should note: As the pressures escalate, you'll probably notice very quickly that things will build to the point where the entire world of your cast threatens to go nova. This is a good thing, and you should at least consider letting it.You are in the business of breaking stuff and finding out what people do afterwards. Be fearless about exploring what happens when everything implodes; the fact that you pushed it that far is a sign you're doing it right. Over-the-top is preferable to underwhelming. An author is a Shiva, a god of destruction - just keep in mind that Shiva destroys so that new things may come into being. So burn it all down, and see what springs up out of the ashes.
Right. Now, a bit more about pressure:
As noted previously, a pressure doesn't have to be objectively big to be sufficient; it only has to be important enough to the characters. Of course, if the pressure involves a need or want for something with little or no significance outside the context of the story, you've got a Maguffin and a particular challenge in making the pressure believable. The Maltese Falcon and the One Ring are the standard classic examples of Maguffins, which just goes to show that it can be an effective device; another one I'm fond of is in Clive Barker's Tyl Eulenspiegel play Crazyface, set in a medieval world where the characters are willing to kill or die for the secret of making chocolate.
It probably goes without saying that pressures can be imposed from within as well, as long as there's something getting in the way of the character satisfying whatever need it is that's creating the pressure. Someone wants to do something they know they shouldn't ought to, or will be censured for, or will face the opposition of another character in; these all illustrate the dynamic that can happen very effectively between desires and obstacles to build pressure. Even boredom can be a source of pressure under the right circumstances (ask any Chekhov character), as long as you're dealing with the right combination of situation and personality to build up enough tension for something to need to happen.
The one thing that truly makes a source of pressure effective is a component of time. In some sense, the clock needs to be ticking down on the characters' situation, or they'll be able to sit it out as long as you can. Don't let them! Even if this time component is itself internally imposed - "that was the last straw, and I can't stand it a moment longer!" - the reader has to be ready to go along with the need for something to happen right now.
This points to another question it's useful to answer for yourself in creating Dramatic Plots: Why is this day different? What happens in the story you want to tell should be different in some significant way from any other day in the lives of your characters, and the sooner you get to that thing the better. That advice you've probably heard about tossing out the first three chapters of your novel, because that's where the real beginning is? Get to the Why Is This Day Different (and the pressure) right away and you won't have to. You don't have to linger over establishing your characters and setting nearly as much as you think you do; dive right into the Martian ship landing, or the caper that goes all wrong, or Johnny Poor Impulse Control finally getting restless enough to do something picturesque to Mr. Higgins.
If you're still stuck on how to jumpstart your plot: One of the best pieces of advice I've read on running roleplaying games is Attack the Party Right Away. If you're not familiar with RPGs, there's a danger at the start of every session where the players will want to wander and explore and get drnk and go gear-shopping before getting down to the business of going on the adventure, but if the gamemaster makes sure everyone gets in a fight right off the bat, this is not going to happen; what's more, the characters get a chance to interact immediately in a high-stakes situation, and you'll have the rapt attention of the players right from the beginning. The same principle works in prose fiction, too. Needless to say, the "fight" doesn't have to be a literal violent skirmish, but the idea of having a high-stakes conflict happen right away (or at least in the first few scenes) has broad application, and may give you additional ideas for building pressure and keeping it on.
One more thing bears mentioning. It's very popular for writers, especially young ones, to claim that their characters get away from them and run off with the plot. Of course, if you're enjoying where they go and the progress of events stays exciting - no worries, and more power to you. But if they're just being stubborn and short-circuiting the story, it's your job to assert authority as author and intoduce whatever pressure you need to get them back on track. Raise the stakes, set off new timebombs, send in two men with guns - do whatever you have to do to keep things moving and the pressure on. You are the author and you are in control, and if you need the characters to be in Cairo on the Equinox, it's your job to make sure the mule-headed little bastards get there on schedule.