The story should be your own. Plagiarism will not be tolerated at any cost. We will know, Big Brother is watching you. 

Judge's decision of prize winners will be final and binding. 

General hints that can be followed are listed below. Feel free to break them if you think doing so will make a better story.

• Although science fiction has the word science in it, it is not the only thing going on.  It can also involve themes of bravery, politics, religion, love, humour, dystopia, heroism, finding the reason of the character’s existence (Existentialism), feelings of connection with the universe and so on.
• A good story can be depressing or awe-inspiring, can haunt you about the possibilities of technology or fill you with hope for what the future holds. Select only two or three of the ideas/themes that I have mentioned in the previous points that you’re passionate about and stick with it.
• Be original. What do you like? What emotional tone do you want your story to convey? Seriously philosophical or light-hearted?
• You can imitate.  Not to be all self-contradictory, but adopting the tone of an existing story or modifying its plot and using it in your own original way will help you express what you want to convey. Artists learn by imitating the style of the masters. Remember though, imitation is different from plagiarism. 
• Check out stories by famous writers like Isaac Asimov (Nightfall and The Last Question), Arthur C. Clarke (The Star and The Sentinel),Douglas Adams, H.G. Wells and so on.
• Use the net.  There are sites that will help you create names of characters, locations or even story titles etc. (Google Character/Location/Title Name generator).