I also have another tip for you--write from your life experiences.
This method actually creates a more higly original story than just taking a variation of a theme. Why? You write what you know. You don't have to write about Paris, New York, Las Vegas if you lived there. You can write about your hometown. To many stories I see is when they take place in a well known city. Most of the time people never visited the cities. But your hometown? People will be delighted if not interested to read about your town. I'm doing a novel for my thesis about the university I'm in now. Most people will never come to this university, but if I write a story about the place I've been living, especially for four years at least, then the reader will feel like he's been there. Same thing for characters and situations.
If you can do that, no one will be able to take your story because of your personality, your mindset, and your and individualistic experiences.
Hopes this helps. 