One of the excessively rigid rules sometimes given to new writers is to avoid flashbacks like the plague. As with many pieces of writing dogma, there’s some truth here. As The Uncensored Writer says:
Flashbacks are amazing and wonderful if done well, sure, but they aren’t always necessary. Sometimes you just don’t need to put one in. An unnecessary flashback sticks out like a sore thumb even if done well.
It needs to give background on character and the plot. It also needs to advance the main plot or the character in some way. If it exists for no reason other than it being a cool scene you wanted to have in there, just cut it[.]
Flashbacks can be an excessively showy (yeah, ‘telling’ has a place too…) way to give information that could be better stated outright, supplied through dialogue, inferred by the reader, or left out entirely.
The strength of flashbacks is in showing psychologically significant prior events, and the emotional resonance of things. Cayce Berryman gives a nice example:
If […] the main character avoids all contact with animals and doesn’t want one, doesn’t want to play with one [s]imply throwing a summarized tip of information about the time he raised a baby bird he found and became so invested, when it died, it felt like losing a child, it isn’t enough—the event must happen so the reader can capture the depth of his pain and current state of emotion so, yes, a flashback is needed.
Flashbacks open a window into the character’s psyche – what meanings are attached to things and people, what events have shaped them. This can give a previously minor feature in the story a weight of associations, explain a character’s reasons for being the way they are, and complicate an apparently pure hero or villain.
With this in mind, it often makes sense for something relevant to trigger the character’s flashback. People remember things in response to sights, sounds, objects from the time, smells, and so on. But this doesn’t mean you have to transition into the flashback using the words ‘remember’ or ‘reminded’, which can come across a bit heavy-handed.
Instead of beginning the flashback like, ‘the Old Spice reminded him of his grandfather, and that time when he was six and…’ or ‘as she waited for her sister to arrive, she remembered their argument last time she’d seen her…’, get into it more smoothly and immersively with dynamic sensory details. Something like, ‘Old Spice had been his grandfather’s brand. He’d been standing on tiptoes to see over the shop counter when his grandfather…’, or ‘as she watched the door in the corner of her eye, she wondered if her sister still had the gothic style she’d adopted around the time of the argument, a red flush shining through her pale foundation as she’d yelled…’.
To transition out of a flashback, a helpful method is to again use an environmental cue, something in the present to take the character out of the memory – someone else walking into the locker room, the sister opening the door.
Some people get confused about the tenses when writing flashbacks. They should be one step back from the tense of your main narrative. If you’re writing in the present tense – I walk – then flashbacks should simply be in the past tense – I walked. If you’re writing in the past tense – I walked – then flashbacks should be in the past perfect tense, which sounds complicated but just means – I had walked.
Depending on the length of the flashback, it can be more effective to only shift back in tense like that for the beginning and end of it, having the middle of the scene be in the same tense as the main narrative. This places the character in the memory as though it’s happening in the moment, being relived, adding immediacy.
If that gets confusing, it may be that the flashback isn’t long enough to do this, or that the setting in the flashback isn’t distinct enough from the setting of the present to make it clear whether we’re in the present or the flashback. Setting the flashback off with italics or some other method might help as well.
Flashbacks can be very powerful when used in the right situation, triggered naturally with well-chosen details to provide immersion and emotional impact.