Does it list reasons for a prologue?
This is my favorite article on when to use a prologue: http://www.writing-world.com/fiction/prologue.shtml
Wanted? A Double Opening
Does your novel truly require a prologue? Unnecessary prologues are a dangerous lot: at best they are ignored, at worst they turn the reader off. Remember, it's there to do a certain job for you, so make sure that a) that job is essential, and b) no one else can do it.
Essential means that the prologue has to contribute to the plot. It has to reveal significant, relevant facts, without which the reader will be missing something. You cannot afford to have your prologue idling away under the pretence of creating an atmosphere. Its first duty is to supply information that is or will be vital to the understanding of the plot.
But that's hardly enough. After all, every chapter delivers key facts, which ultimately amount to the plot. What makes bits of information require a prologue? Any number of reasons. Perhaps relating them in the body of the novel would cause a breach in point-of-view etiquette. Perhaps they occur in another time or place, and have too much weight to mention by-the-by. Or they might choke the narrative to death with background details. Any of these cases, and some others (which we'll soon discuss), call for a prologue.
To make sure your prologue works well, you can put it through a simple two-step test: try to leave it out and see if anything important is missing; then try to change its title to "Chapter One", and check if the plot integrity is damaged. If you've answered both questions with a yes, then your prologue is doing a good job.
What can a prologue do for you? A basic acquaintance with literature will yield four major types of prologue, each with its own specialties. They are: "future protagonist", "past protagonist", different POV, and background.
Job description: "future protagonist"
The "future protagonist" prologue shows the hero or heroine some time after the main part of the plot has taken place, and is written in the same point-of-view and style as the rest of the novel.
In third-person POV, its primary use is to give the end of the story first, while the novel itself explores how things had come to pass. A good example is "A House for Mr. Biswas", by V.S. Naipaul, where the prologue begins several weeks before the protagonist's demise, while the first chapter backtracks to just before his birth.
In first-person POV, you will usually find the protagonist sitting and writing a memoir, or explaining why one must be written or told. The tone is usually personal and reflective. The emphasis is on the protagonist's own impression of the past, whereas the actual end of the story may be only alluded to. Such is the case in Umberto Eco's "The Name of the Rose", where the prologue introduces Adso at an old age, thinking back to his youth when he and his master William had solved a mystery at an abbey. Adso's account gives us a background of the era, and his own impression of Brother William, but in no way hints as to how the mystery was solved.
Job description: "past protagonist"
The "past protagonist" prologue is generally used when the protagonist has a defining moment in his past which must be known to the reader, in order for the reader to understand this character. Think how cold and alien Batman would be, if we hadn't first seen young Bruce standing bewildered over the bodies of his parents.
Often, trying to cram such an event into a flashback would considerably curtail its importance and strength. Relating it in detail in the prologue has two advantages: it sets the novel in motion with a strong, usually emotion-charged event; at the same time, it creates an immediate affinity towards the protagonist. It can be done both in first- and third-person POV.
Job description: "different POV"
A different POV prologue describes a certain event from a point-of-view different than the main characters of the plot. This event may occur in the same time-frame as the plot, or years before or after. Its relevance may be made clear in the course of Chapter One, or Chapter Thirty-four. However, it must have a relevance, which will affect the plot substantially in some way (otherwise it's idling away). A different POV prologue should be written in third-person, even if the novel is in first-person.
This sort of prologue allows you to pull off many plot-twists, without having your readers screaming "deus ex machina". In other cases, it allows you to introduce a danger of which the reader should know, but the protagonist shouldn't -- yet. For example, you can have the villain lay out the fate he has in store for the hero, and then begin Chapter One with an unsuspecting protagonist, who is now likely to elicit concern rather than boredom.
A master of this type of prologue is Clive Cussler, author of many best-selling adventure novels. He uses it every time. In "Sahara", for example, the prologue follows the struggle for survival of aviatrix Kitty Mannock, after her plane crashed in the desert. Her story remains unfinished and its relevance unexplained, while the plot switches to Dirk Pitt -- Cussler's eternal good-guy -- in his endeavor to prevent a worldwide ecological disaster. Not until three-hundred pages later does Dirk Pitt stumble upon the remains of the plane, which he utilizes to escape certain death. It works, both for Dirk Pitt and the reader, only because Cussler had established the plane's background in advance.
Job description: "background"
A background prologue can usually be found in the science-fiction and fantasy genre, where the settings may differ so wildly from our own world, that without a proper explanation the reader might get lost. Trying to explain such settings as you go along might slow your pace to a trudge. The line is hard to draw. On one hand, you cannot require the reader to wade through an essay of history (or future-history) as soon as he picks up the novel. On the other hand, you cannot throw him into deep space and expect him to start flying. Of all types of prologue, this one is the most risky.
The key is to create a balance between information and interest. You can do this by telling a simple story, plot-wise, which will demonstrate to the reader the mechanisms of the world. Such a narrative would usually follow the lines of a "different POV" prologue, with emphasis on exposure rather than on intrigue.
In Heinlein's Time Enough for Love, the body of the novel follows Lazarus Long as he recounts highlights from his three-thousand-year-long history. The prologue is written like a historian's preface to a published memoir, and analyzes the credibility of the events therein. Along the way it explains how people have come to live so long, and how this had affected human society. It also gives background about Lazarus Long, which makes the reader look forward to meeting this character "face to face". The preface is signed by the Chief Archivist of the Howard Foundation, which makes the reader feel as though he'd just burrowed a book from a future library. When the reader meets Lazarus in Chapter One, he knows roughly where he's standing, and he's free to concentrate on the chain of events.
Any workplace has a list of dos and don'ts; the prologue is no exception. Here are some:
The prologue should always be an integral part of the novel, written in the same spirit and style. Otherwise it's a personal preface rather than an opening chapter.
The prologue should read like a short story in every aspect, except for its ending. Rather than resolving all conflict, the end should leave the reader intrigued. Any conflict created in the prologue, however, must be resolved somewhere along the plot.
The prologue should start with a strong and intriguing hook as if it were the only beginning of the novel. This does not exempt Chapter One from beginning with an equally strong and intriguing hook.
The prologue must stand out from the body of the novel in at least one fashion: the time of the events (which should be stated both in the prologue and in the first chapter), the POV character, and so on. The reader should feel a distinct switch in his mind when he begins reading Chapter One. And just as important, he should never experience the same switch again within the novel. For example, if the difference between the prologue and Chapter One is an interval of five years, you may not fast-forward time again within the novel.
The one exception is a novel wherein the point of view shifts between several characters, and the prologue is a "different POV" type. In this case, the switch between the prologue and Chapter One is bound to occur many times throughout the novel. You can keep the prologue distinct by assigning it to someone outside the group of POV characters. Later on in the novel we may meet him once more, but never see things through his eyes again.
Necessity, content and form -- if your prologue is a professional in all three, then you have acquired a superb worker. Now you can begin doing your own job: telling an interesting story to your readers, and taking them all the way to the epilogue.