Mostly practical advice, again, but a lot of fantasy prologues are in sorry shape, so that practical advice might be needed.
1) Do not make the prologue too long.
I personally use a cut-off point of about five pages, or a little shorter. I’ve seen books with prologues that were much longer and still worked, but in any case, the prologue should not be longer than a chapter.
Why not? Three reasons:
a) If the prologue is in the tradition of most fantasy prologues (see my complaints below), then it delays the main action of the story rather than contributes to it, and prevents your reader from meeting and becoming interested in the main characters.
b) Most people will assume, rightly or wrongly, that the prologue is less important than the first chapter, and get impatient when it stretches on and on.
c) Not starting the story with Chapter 1 makes it seem as if you aren’t really starting the story yet.
On the heels of that…
2) Consider if you really need a prologue at all.
If you start the story with your main character from the beginning and always stay in his or her head, I don’t think you need one. If you are talking about events that don’t become important to the story until a long time after, then you may just be info-dumping, giving information that should be woven into the narrative instead. Examine why the prologue is there. What does it really add to your fantasy novel that a first chapter won’t?
Of course, a lot of prologues in fantasy novels are there for certain specific reasons. I’m going to discuss the different kinds of prologues I remember seeing below, and the problems with them.
3) If you have a prologue that tells a myth or legend of your world, try to make sure it’s actually relevant.
These can on occasion be done well- look at Tolkien’s first part to FOTR that tells a lot of history about the hobbits, or Guy Gavriel Kay’s prologue of the Fionavar Tapestry that tells of the imprisoning of his dark lord, Rakoth Maugrim- but don’t always work. (I’ve known a lot of people who got bored by “Concerning Hobbits” and never read further in Fellowship of the Ring.) It can be very annoying to read about the exploits of gods and the hiding of some treasure or the telling of some prophecy, and then leap straight into the life of Ordinary Peasant Hero 2,876,942 with no indication of when the gods, prophecy, or treasure will come back. These are also the kinds of prologues that suffer most from the author’s temptation to info-dump. Yes, you have to establish a lot of information about the fantasy world, but no single prologue or chapter should be an excuse to just talk and talk and talk about the legends, history, or theology of the world.
Finally, I find that a lot of these prologues don’t work for me because the authors have no grasp of mythic language. They come off sounding like bad pastiches of the Bible or Greek legends, and such things don’t make for an auspicious beginning to your story.
4) Try not to have such a large gap between the prologue and the first chapter.
Even when the prologue has ordinary human beings and not gods in it, they tend to talk about prophecies, or sometimes someone kills another person, and then the “story proper” begins hundreds or thousands of years later. Again, this can be very irritating. What’s wrong with beginning with your main characters, the ones the reader is actually supposed to care about, instead of these people who only show up briefly and then vanish? Even if they come back, it’s usually not until far into the story, causing yet another annoying disjunction as the reader is ripped from the main character’s story into trying to remember something about the wizards in the prologue.
Done badly, these prologues also suck all suspense out of the story. If the hero is searching for the Golden Cup of Weebledom, and the reader knows from the prologue that it’s hidden on top of Doom Mountain, then there’s no surprise, no involvement with the hero’s quest as quest. The reader already knows the end. “Yes, it’s hidden on top of Doom Mountain, how exciting…only not, since the prologue told me that already. *yawn*”
5) Avoid the annoying pattern of telling some traumatic event from the hero’s life in the prologue and then skipping to ten or twenty years later in the story itself.
This is supposed to make a good transition because it avoids having to tell the traumatic event in flashback, and also shows the reader how the hero is dealing with whatever happened. The problem with it is the same problem that always haunts characters who are the victims of the author’s Drive-By Trauma shootings: it presumes the hero or heroine has never started healing at all, just remained locked in the grip of the almighty trauma. Even if a heroine’s entire family was slaughtered before her eyes when she was eight, by the time she’s twenty-eight, I would have expected her to stop dreaming about it every night and screaming whenever she saw blood. If she hasn’t, there is something seriously wrong with her. And no, I don’t believe that that kind of psychological wound can be healed by discovering she has magic and a destiny, either.
If you really want to show someone recovering from a traumatic wound, then I would say the best bet is to begin the story no later than six months to a year. And if you want to keep the hero from knowing what really caused his companion to be so silent and taciturn, then I suggest not showing the companion’s trauma in the prologue, either, lest your readers, who are in the know, start thinking the hero is stupid for not figuring it out.
6) Do not, under any circumstances, create a prologue that is only relevant at the end of the third book or just a little earlier.
This is one reason, I think, why Tolkien’s “Concerning Hobbits” does work; it doesn’t detail a race of people we only meet when the heroes stumble into their hidden little land in the second book, but a race who are the heroes, and whom Tolkien wants us to know and recognize from the beginning. On the other hand, I have read many fantasy books where the wizard hides some treasure away and then show up and make some dramatic announcement only near the end of the second book, by which time the audience has forgotten who he is. How many times have you encountered a dramatic announcement in a fantasy book and reacted with, “Who? What? Why does that matter?”
I can tell you how many times I have: too damn many. And I have a pretty good memory, enough that I don’t usually need a character index. When an author pulls this kind of trick, it’s a sign of sloppy worldbuilding, and once again, using the prologue as a dumping ground for information instead of an actual part of the story.
7) There’s nothing wrong with having the prologue detail an ordinary event.
Really. There isn’t. The heroine can go out picking flowers with her mother, and perhaps see a cave that she’ll go into in a few chapters, and it will be okay. She doesn’t have to find the sword of Arcadia right then, or see her mother slaughtered in front of her eyes and have the story begin when she is a far-too-obsessed-with-her-mother adult. I think that prologues make wonderful foreshadowing devices when the foreshadowing:
a) is buried in the midst of something else, so it doesn’t seem as if the writer wrote the prologue only to hold the foreshadowing.
b) is not heavy-handed.
c) is made relevant again within a few chapters.
Prologues have their place; they are just misused so fucking often.