The flash-forward, a little-used fiction technique, gives your readers a glimpse of the future:
Alison wanders through her new house, wondering how she will possibly fill it. Her sofa and coffee table look like doll furniture under the cavernous ceilings. Even the light switches look foolishly small against the broad white expanses of wall. Twenty years from now, missing the husband and children she does not yet know she will have, she will wander through this same house wondering how she will possibly empty it.
A flash-forward hurtles your readers ahead in the story, sometimes too fast. Flash-forwards can add poignancy and weight to a character's situation, but if you have no compelling reason to telegraph future events you risk being (rightfully) accused of gimmickry. In the preceding example, Alison is a character who is always looking on the other side of the fence, so the brief description of her future is probably appropriate.
Ironically, flash-forwards do not have to be rendered exclusively in future tense. In my novel, Secret Language, I use one flash-forward, during the present-tense wedding of Faith, the main character. Faith is remote and wary, terrified of life's ordinary joys. At her wedding, she "steps out of her body" to watch from a safe distance:
. . . Heat bears down on her from all sides but she cannot warm herself. She's gone cold with the fear of love and the knowledge of her unbelonging, so cold she can barely stand, and so she removes herself from this joyful gathering, steps away from them all while her chilled body stays.
She watches Joe slip the ring over her knuckle. She watches herself murmur "I do," all the faces tensing forward because they cannot hear her.
She will remember this moment many, many times. Remembering, she will believe that if she had only been able to warm herself, if she had only stayed inside her body as she pledged forever and true, she might have learned to live with a man like Joe, a man who loved her.
The movement of tense in this passage is deliberate. First, I move from present tense to the future tense of the flash-forward ("She will remember this moment. . ."). Then the flash-forward itself becomes a passage in which a mini-flashback takes place ("if she had only been able to warm herself.. . ."). This is tricky; I am telegraphing, through flash-forward, a scene in which Faith will look back. Why did I complicate the passage like this? Because the novel is about Faith's journey toward an emotional place where she can finally "warm herself and indeed "learn to love a man like Joe." Faith is a woman who refuses to live in either the past or the future, only the present, and to place her in both the past and future in this passage serves as a pivot point in the novel. It was the best device I could think of to describe this paradoxical, elusive character. At this point, where flash-forward and flashback converge, the book takes a sudden emotional leap forward.
In our story about Sparky the dog, the flashback became the story because the frame (the mother's funeral) was less important or interesting than the flashback. If you insisted on using the mother's eventual death as a way of adding weight to the story of the boy's ninth summer, a flash-forward would do nicely:
By morning the dog was dead. He was lighter than I expected, his fur still smooth. I followed my mother to the section of our land that looked down over Blue Creek. Tearless and solemn, we buried Sparky next to a growth of mustard flower. My mother let me fill the hole and mound the iron-red earth. The spade was one she sheltered at the back of the toolshed, for it was little-used and almost beautiful: sharp and solid, with a thick handle fashioned out of a light, burled wood; the very spade I would use ten years later at an occasion no less solemn but marked by many tears.
Flashbacks and flash-forwards are satisfying descriptive devices, but beware of using them unless you can articulate your reasons. "To fill in information" is not good enough. You can fill in information a little at a time during the natural forward course of the story. Ask yourself every time: Why am I flashing back? To endear the readers to a not-yet-met character? Fine. To contrast a character's present husband with the former husband? Sure. To create a context that will resonate in a reader's mind as the story progresses? Sounds good. You can probably name a dozen good reasons for using flashback, but if you can accomplish your goal without one, why not save yourself the aggravation?
A WORD ON THE SET PIECE
A set piece is a detour in the path your story takes. It is a fixed descriptive diversion executed with great care: an elaborate description of a horse farm, for example, or a brick-by-brick account of the building of a museum.
Digressions are fun. You're writing about a character in a terrible emotional crisis, and all of a sudden the circus comes to town and you find yourself devoting four and a half pages to the elephant act. Such a set piece can be brilliant and beautiful and a pleasure to read, even if it appears to have only a marginal connection with the rest of the story. If you're going to stop the story's present action, then stop it big! Like a well-crafted flashback, the set piece can take on its own momentum.
A good set piece only seems irrelevant to the story at hand. A two-page description of the way rain moves across the prairies may seem like a mere literary detour, but in fact it telegraphs the swift changes that are about to befall the character in the story. A set piece about the building of a skyscraper may be entirely appropriate in a story about a woman building a medical practice, or a parent building a relationship with a difficult child. Also, a set piece may suggest how a character thinks, what a character's moral limits are, and so on. In a story about a retired nurse longing for a more interesting life, the set piece about the circus might highlight the fanfare and theater of the trapeze act. In a story about an ex-con, the same set piece might address the cruelty of forcing animals into cages.
If you find yourself caught up in a set piece, make it count. The description should be delectable, with lots of little-known facts and details that will dazzle your readers. A tour of your grandmother's living room (unless she lives in an igloo or a culvert) probably wouldn't make much of a set piece, but a description of wine-making in Napa Valley might. Readers aren't too cranky about diversions as long as they learn something in the process—something delivered with a descriptive flair, that is.
Finally, be sure the story—or novella, or novel—can support the weight of the digression. A ten-page story can't support a four-page set piece. A ninety-page novella can. A novel, of course, is the roomiest place to peer down those roads not taken.