Building a believable storyworld is crucial when writing fantasy, SF, paranormal, magical realism, or any other sort of speculative fiction. Naturally, your storyworld will be influenced by the worlds of your favorite authors and filmmakers and storytellers in other media, but you want to avoid mimicking them so closely that your work sounds like fanfic. But how do you avoid that, when those beloved storyworlds are so compelling and vivid in your mind? When your muse speaks so loudly that you can’t hear the voice of your own creativity?
Let’s begin by focusing on three categories of things you do not want to do.
The first is simple plagiarism. Never re-use proper names and specific terminology (so a general term like “hyperspace” is okay but “hyperdrive motivator” can’t appear in your story).
The second is structural. Don’t copy the most-famous plots too closely, especially those plot twists that are iconically connected to those movies (so your protagonist cannot discover that your antagonist is his father, especially not during a duel). This is not to say that you can’t follow any of the same story arcs: please do! Just weave your plot in your own way.
Another structural pitfall is having the same cast of characters but with different names and some gender swaps. Sure, certain character roles are common: protagonist, antagonist, contagonist, mentor character, comic relief, etc. But if you’ve copied your source so closely that a beta reader says “I think your ‘Han Solo’ character’s sidekick should be taller and hairier,” you’ve crossed the line.
The third thing to watch out for, and possibly the most difficult one of all when you’re still early in your writing career, is simply your use of language, your wordcraft. This one can go very well, or very badly: Alison Croggon clearly riffs off Tolkien’s worldcraft and wordcraft, but no one ever says that in a disparaging way. David Weber openly credits C.S. Forester’s influence, and consciously re-casted Forester’s Horatio Hornblower series in the brilliant Honor Harrington series, even to the point of preserving the main character’s initials and coming up with space-age versions of “sailing tactics,” and his fans think all the more highly of him because of it. But lesser authors can easily sound just like their muses, except …worse. The classic “young-punk-writing-his-own-sequel-to-Infinity-War-except-you’re-not-supposed-to-guess-that” kind of thing.
The more you write your own stories, in your own worlds, the more you’ll develop your own voice as you describe and explore them.
Eventually, you’ll be compared to your muses in a favorable way… and contrasted with them favorably too.
(You can find the rough draft of this post as a Quora answer here; other competing answers to that question might give you additional helpful insights!)