This is the rant on making a stand-alone novel. And this one has a lot of Guy Gavriel Kay in it, since, unusually for a fantasy author, nearly half his books are stand-alones.

1) Set up a central story-core.

I’ve compared fantasy series in the past to a vast tapestry. The author weaves the threads of story, characters, plot, backstory, description, outline, and so on together to create something that, although it may have dozens of subplots, is meant to be appreciated as a whole structure. The whole point of epic fantasy—at least, the good kind—is to have the virtues of grandeur. The space and the sprawl let you tell stories that you can’t in a single novel. (It also, unfortunately more often, seems to encourage authors to tell stories that don’t need to be told at all, but that’s long years of bitter experience talking. I will think happy stand-alone thoughts instead).
With a stand-alone fantasy, there should still be an attempt to use fantasy’s strengths—the passion, the imaginative freedom that realism won’t let you get away with, the ability to play with history and metaphysics that may be entirely different from our own world’s, and so on—but I think the structure has to be different. One way to conceive of it is to see the story as a story-core, an overriding idea behind all the subplots. The metaphor I think of isn’t a weaving, but a tree with many branches. The small stories are the fruit hanging from the branches. Unlike a multi-volume series, where the subplots may duck in and out of each other, in this structure they share similarities with each other, but ultimately depend on the story-core. Any connection between the subplots is an excellent bonus, but they don’tneed to constantly touch as I wish they would in more epic fantasies. They can reflect on each other by the very similarities they share.
The Kay stand-alone that does this best is Tigana. There are dozens of things going on in the book, including subplots of rebellion and kingship and vengeance and conspiracy and magic and incest, but they all turn on the central story-core: the theme of memory. Kay acknowledges this pretty explicitly in his own afterword to Tigana (only minor spoilers). Memory of what’s lost is reflected in the central political conflicts, but also in the way that characters do everything from drink wine to have sex. I find it very hard to imagine the story of Tigana sprawling across several books (though see point 5). Stretched over several books, this theme would weaken, and others would need introduction. As it stands, it’s just right for a single, self-contained story.

2) Choose your characters wisely.

Many fantasists turn as if by instinct to a cast of thousands. It doesn’t mean the instinct is wrong. It does mean that the instinct should be questioned, particularly if the author in question plans to write a stand-alone novel. Do you need a cast of thousands? Why? More to the point of the rant, if you introduce those thousands, doesn’t that mean some characters are going to get short shrift, since you won’t be writing 1500 pages about them?
I’ve read far too many stories where characters got lost along the way. The author tried for an ensemble, and couldn’t handle it. Or she divided her narrative into multiple “storylines,” each of which contained many, many globs of gooey character backstory; people spent more time talking about their pasts than they did moving the plot forward. Or the author promised that such and such a loose end would be resolved in a full confrontation scene at the end of the book, and then wound up tossing in a throwaway line about the character meeting her abusive father again after all these years, reconciling with him, and going away happy.
Bad authors. Go back and try again.
There is nothing that says fantasy necessitates a world-spanning story. Create a quiet and personal one in a wonderfully realized environment, by all means, and show that environment only from the corner of the characters’ eyes. The plot won’t be about learning every random peasant’s backstory, nor about saving the world, but learning the backstories of those three or four people who dominate the novel or saving that one corner of the world.
Kay introduces quite a number of characters in Tigana, more than I’d usually expect to see in a stand-alone, but he’s a good writer, and the book is rather long, nearly 700 pages. Also, every character he chooses connects back to the two main factions—the party trying to bring back their lost country, and the sorcerer-king, Brandin, who took away the country’s name and smashed its legacy in the first place—or is ended sharply, such as by death. When he takes off in the middle of the novel to explore someone’s midnight adventure, he does it with people who by that point the reader has known for 300 pages, not some random new stranger. People do show up for shorter scenes, but they have less history.
It’s arguable about how well this technique actually works. I’m one of those people who think that Kay’s focus on Brandin and his concubine, Dianora, is by far the strongest part of the novel. He actually makes his rebels/revolutionaries thoroughly unlikable in some places. But he doesn’t fling people off random cliffs, and he doesn’t lose track of his characters.

3) Don’t use the stand-alone as an excuse to tell us more about the setting than the story.

Sometimes an author panics. “Oh, no! I want to write a stand-alone book of only 500 pages, but since this is the only chance I’ll get to play with this world or these characters, I have to make sure the reader knows all about it/them!”
I’ve complained before about beginnings that slam the reader over the head with an infodump. That’s usually caused by the author’s insecurity and lack of trust in her readers. At least in a series, the author has the mitigating idea that she’ll get to tell some things down the line, in another book, so she might not feel compelled to push everything at you at once.
If the author goes into panic mode in a stand-alone, watch out. “They MUST understand everything, since I won’t be returning!”
Well, see, no. No, we don’t have to.
I hold out for complexity and complication in all things, usually. But at the same time, I have to bow to reality. Fictional characters aren’t as complex as real people; they can’t be. Nor can a fictional world have the same weight and depth of history as our own. But they can look like it, and I wish more people would strive for that look than just regurgitating whatever glurge they’ve picked up from elsewhere.
The stand-alone novel is your chance to cheat all over the place. Instead of taking a precious page out of your sole 500 to explore every corner of a city, and another page to talk about its history, and another to make sure the audience knows what the protagonist’s inn looks like, hint. Leave innocent bits of the larger world or story, or of the characters’ pasts, lying around. The reader will pick up the bits and assemble them into the larger picture. That picture may be airier and lighter than a fantasy world built up over three—or five, or ten, or thirteen—books, but air and light suits the stand-alone, rather than overwhelming lushness.
Kay does this everywhere. In The Lions of Al-Rassan, he doesn’t give his readers a treatise on the making of Asharite (the analogues to the Moors in his version of al-Andalus) poetry; he gives a few examples of the poetry instead. He refers to the city of Ragosa as “ivory” a few times and describes its culture and gives us a view of the king and his Kindath (analogue to Jewish) prime minister talking. This is much better than a droning history of how and when it was founded. A bandit on the brink of death thinks he sees death coming for him as a pale, dark-haired woman, a solid image that doesn’t depend on a paragraph of “Here are the superstitions of death among the mountain bandits.”
Admittedly, one can overdo this; I found Kay’s breaking away from his main narrative to follow minor characters about in The Last Light of the Sun a tad bit unconvincing. And some people might argue that Kay can cheat all he likes, since he writes historical fantasy and so can rely on whatever knowledge of the place and period his readers are carrying around with them. So what? Go find your own way to cheat and hint and not overdo it.

4) Make a graceful ending.

Yeah, yeah, not a problem, right? You’ve got your theme and your characters and so on, and you know what you’re going to do with them.
Except that letting your story gallop around as if you were writing a series, and then tugging it up at the end, all panting and sweating and blowing, does not make for a graceful ending. It makes for an awkward one at best, and, in the worst cases, a rushed ending, where the author pulls the throwaway line trick from point 2 and has an epilogue that neatly explains everything.
Fuck that. The stand-alone is not a poor substitute for a series. It’s its own form, and it follows its own rules.
You’ll need control of several things as you approach the ending, and only one of them is the plot. You’ll need control of the pacing, first and foremost, so your ending doesn’t rush. You’ll need a balance of “The story ends” and “Life goes on,” so there isn’t too much of a pat resolution to every storyline or the sense that the plot is trailing disconsolately away into the distance because you really wanted to write a sequel. (See point 5). You’ll need a willingness to leave your major characters at a point where they’ve reached some kind of resolution. And you’ll need an ending that gives the story-core its due, and doesn’t fell it too soon.
You can do things with a stand-alone that you truly can’t with a series. Don’t let the perils of ending it stop you. At least, if you end it, there is absolutely no way that your world and characters can develop Series Rot, as Salvatore and Hamilton and Jordan and Eddings and Brooks and countless others have done. The next book will also force you to start over in fresh woods and pastures new, which is a great way for jumping out of a rut as far as storytelling itself goes. I’m of the opinion that people should switch stories more often, if they can. A great brooding epic that eats your life is a grand thing to have, sometimes, but it can also crimp the author’s style to that one story, and limit the strengths she’ll develop if she explores in other directions.

5) Shake sequelitis.

This is the belief that a story MUST have a sequel, it simply MUST, because you haven’t told the story of the main couple’s children yet, or the second time they defeated the Grand Evil, or the time their second cousin’s mother-in-law’s best friend’s dog ran away.
Wake up. Not every story has to have a sequel. Control your ending, and your stand-alone is a lovely little thing, complete in itself. It does require greater commitment to process and finishing than a series does, but so? Just because you’re growing a bonsai tree instead of a forest doesn’t make it less a work of art.
This is true even of stories that may seem to need a sequel. Kay does a daring thing and ends Tigana in such a way that three characters—though, let it be known, minor characters, not major ones—are poised on a cusp of change. It comes at the very end of the epilogue that’s just set up nice, neat, patterned little lives for them, and is thus the most effective bitchslap to the overly completist fantasy epilogue that I’ve ever seen. Kay’s stated firmly that he will never write a sequel to Tigana. There are people who hate him for that. I don’t think he cares.
Stand-alones can create characters who will live after the story is done. In a series, that’s often not the case, because a) the time-span covered is often much greater, b) the author is obsessed with creating a structure that ties together everything in the fantasy world, and c) the author feels so invested in the characters that she wants to know what’s happened to them forever and ever, even after she stops writing about them. (I’m convinced this is why so many fantasy series end with so many characters either dead, or married and happily producing babies).
For all that a stand-alone fantasy has to be self-contained, that means self-contained to other books. It says absolutely nothing at all about turning the characters into cardboard cut-outs when you’re done with them. I think it’s more accurate that characters in a stand-alone fantasy are done with the author. Give them to the wind and the light, and let them walk on into their lives, and don’t insist that there has to be another story about them. Those other stories will be in the readers’ minds and imaginations.
Because Kay is my favorite fantasy author and I am shocked and appalled that he’s not better known, here’s the main URL of his site. And the reading passage that serves as a sample of Tigana (no major spoilers). And the reading passage from The Lions of Al-Rassan (brief spoiler about a minor character).
/end plug moment.