Read through your finished story from beginning to end with a red marker. Circle any parts of the story that you have read before or seen in a typical fantasy movie.
Think about how you can turn your plot on its head by introducing completely new elements to your story. Take a few nights and record your dreams. It will help you to gain a more whimsical and surrealistic point of view that you can perhaps use in your fantasy story plot.
Revisit the story after a few days of dream recording and see what you have to contribute to your plot line. Set your fantasy story millions of years in the future or even on a different plane of existence. Give your character traits that are not remotely human, like having to breathe water, or sleep in the cups of flowers. Be as imaginative as possible when trying to find new inspiration.
Reread your most favored fantasy stories and identify what about those stories feels the most attractive to you. Create your own creatures as opposed to relying on the creatures typically used in fantasy stories (elves, dwarves, fairies, etc.). Develop new classes of creatures with distinct features and whole back stories to help make your story more original.
End your story differently than most fantasy stories, which might mean a sad ending. Consider giving your story a darker and less clichéd ending. Of course you can always write sequels until you have resolved the conflict. Write mini-stories surrounding your characters to give them depth and dimension, outlining their lives, lineage and struggles before your book even begins.