It has been said that there are only thirty-six basic plots in existence, that there is nothing new under the son, that everything has been done before. This can cause issues for both readers and writers who are always looking for the next great, original story. One that takes them places they’ve never been before (or at least takes the familiar and skews it in a different way).
I think the main key of originality is to stop worrying so much about being completely original. For an example of the same premise being written originally by many different authors check out What the Wind Picked Up. It isn’t speculative fiction, but it does prove a point. YOU are a key factor in making any writing done original, the fact is no-one can write a story the same way that you have.
But there is also another way to ensure being original.
Don’t just go with the first idea that pops into your head when something is coming up. Take that idea and look at it carefully, then see how you can twist the conventional thoughts on those into something believable yet uncommon.
Do this with your characters, your plot points, your ultimate goals. Even if you are writing a basic heroes journey tale with a young, farming lad pulled into a quest to wield an ancient artifact and save the world. Finding little twists to make on the characters and trusting your own instinct will provide a work that is unique.
And don’t be afraid to read widely in the genres, you won’t suddenly pick up all of the unoriginal ideas and have them bleed into your writing, but you’ll come to recognize the conventions that are becoming cliché’ and maybe think of interesting ways to twist them.
There will always be parallels and similarities within the works of those raised in the same culture with the same artistic influences and grand social experiences. But it is the details that make one work just a mimic of an older tale, and one that forges new territory.