A large part of foreshadowing is implication. Writers have been known to confuse foreshadowing with plot exposition such as telling the reader, ‘Doing X could end the world’. While we’re revealing a potential outcome of the story we’re not foreshadowing the ending we’re telling the reader the stakes without which the story couldn’t function. In Pride and Prejudice by Jane Austen we’re told that the Bennett estate is entailed to Mr Collins, therefore the Bennett women must marry well to achieve security. In Lord of the Rings we’re told Sauron could use The One Ring to rule them all. Without knowing these the story would have no momentum because there would be nothing for the character to strive against.
When we foreshadow we’re implying outcomes to the stakes. Elizabeth Bennett needs to marry but who will she marry? There seem to be some sparks with Darcy’s cousin but does she seem to be changing her opinion of Darcy or will she not marry at all? The Fellowship needs to destroy the ring but how will they do it? Or is Frodo being corrupted by its power and won’t destroy it? As such we can both imply outcomes and thereby racket up the tension. In the case of Lord of The Rings we know we’re reading a story of good triumphing over evil but will that triumph be at the cost of Frodo?
These moments can be created through conspicuous foreshadowing, such as other characters noting a change in Frodo’s behaviour, but we need the moments of implication to bolster these. Characters observing change doesn’t work if we don’t show that change which is where the implication comes in. Throughout the story we can see a character’s changing perspective through the way they behave, perhaps they become more or less selfish, perhaps they begin to show affection towards another character, or perhaps someone reacting more or less aggressively then they did before. These changes can take place gradually through the course of a story and the reader can begin to notice the change before the change is stated. In the case of The Lord of The Rings the change in Frodo becomes evident to the reader before any of the characters comment on it. However, the change is not so obvious the reader immediately begins to assume that he won’t throw The Ring into Mount Doom.
Slight changes in behaviour and speech can be subtle, or sometimes not subtle if we choose, indicators of changes that could potentially affect the outcome of the story. This could be a seemingly small gesture, such as someone sharing their food, or a huge dramatic moment where the person who isn’t a ‘hero’ turns back to rescue someone. However, a dramatic change is often most effective when there are smaller ones preceding it.
It was something I had to think about carefully when I was writing Lot’s arc for Victorian Mistress in particular because I needed to indicate Lot changing without Lot, a first-person/subjective narrator, necessarily noticing the change but the reader could. As I showed in my self-editing articles it wasn’t something I got right the first time, I had to experiment with different things to find the best method of implication, so you don’t have to worry if it doesn’t seem right on the first attempt.