Those of you who have followed Scribbles since pretty near the beginning are already aware that foreshadowing is one of my favorite aspects of writing. It gives me a thrill to read a book, especially one familiar to me, and catch a new instance where threads of future scenes are woven into earlier sections; I love it when the first book of a series plants seeds for those that follow. I am not sure why, save perhaps that, though (and perhaps because) I am a writer myself, it never ceases to amaze me that an author's mind can contain such a monumental and complete thought. It is one thing to start at the beginning and bumble clumsily to the end; it is another thing entirely for the ending to be foretold by the beginning.
There are many different styles of foreshadowing. One of the most obvious is that of premonition or deja vu, two phenomena we don't really understand, but that serve us well as writers. They allow us to give the character a hint of whatever disaster is to come - not a vision, for that tends to ruin the suspense, but an unpleasant and indefinable taste. And through the mind of the character, the reader feels it as well.
Foreshadowing can also be done in less obvious ways, ways that will probably not be noticed until the second reading when the ending is already in mind. They can be as slight as a word that a minor character uses, a change in the weather, an insult, the writing of a letter or the killing of a moth. It can be anything, really. There is nothing so slight that the mind cannot latch onto it, connect it with an event and rethink it months or even years later. The association needn't even be direct; it may be a connection may be only in the character's mind. Personally, these are my favorites because of the detail and nuance they reflect - and because they're even more natural than a premonition.
As splendid as foreshadowing is, however, it is but one side of the coin of continuity. Foreshadowing is what the writer does at the beginning of the novel; it is the darkness cast by the real event to which the author was looking. But later on, especially in a long novel, it is necessary to harken back to earlier scenes and bring them clearly before the reader's mind again. I call this echoing; like as not it has different names in different places.
At any rate, for me these are usually pointed (often unintentional) repetitions of something that happened many chapters before. Again, they're usually small things - the flipside of foreshadowing. A phrase might be reused that harkens back to another scene; a character's expression might remind the narrator of someone else; a color might be tied to something critical. Whether indirect or direct, it is an association that carries the mind back across the pages even more plainly than foreshadowing carries the mind forward.
However they are used, foreshadowing and echoing are wonderfully tantalizing ways of bringing together the pattern of a story. And on a rambling side note, they represent to me one of the spectacular aspects of the Bible: no other book in the world so reflects the perfect continuity in the mind of its author. Perhaps, after all, that is what we all pattern our own writing after.