I too am an amatuer writer and author wannbe, but the greatest advice I heard from a friend who has a couple books out. He told me "Write your story from your heart, not with your mind." This means, for every story you write, forget about the rules of writing. (Grammar, spelling ect.) There will be time to clean it all up later, besides that is what proof readers are there for. LOL
You may want to write a biography of your characters, what they are like, what turns them on or off. When and where were they born, where did they die? family members, and relatives. You want to get to know your characters cause they have to be as real as you know other people.
Your stories should come from within, not forced out, not to be over theorized about if this or that is possible. Always trust your imagination for your stories.
With a couple of my stories, I actually play them in my mind as if they were a movie. Writing down as fast as I can what the action of the "movie" is, and the dialogue. When you take a bath or shower, use that time to play your "movie" (besides nothing else you have to worry about distracting you in there.)
And above all, bring real emotions in your story. If it makes you laugh, it will make others laugh. If it makes you cry, others will cry. Unless your a vulcan, then can't help you there.
Oh and have fun with your story....