Keep a notebook. Write down things you see or hear that you feel might make an interesting story. Jot down ideas for titles. Make notes on people you see, including brief physical descriptions and character traits. If you find yourself in a writing slump, refer to this notebook to help spark a story.
Outline your story idea. There's a difference between story and plot. A story is the "what" aspect and plot is the "how" aspect. A man and woman meeting and falling in love is a general story. There are countless ways that story can be plotted. Outline how you will get from point A, when man meets woman, to point D, when they get married. Points B and C need to contain a little conflict to make the story interesting--something that appears as if it will prevent the couple from getting married. The conflict and how they overcome it is what will make your made-up story interesting enough to read.
Write your story according to your outline, but be open to changes. Sometimes a story will seem to take on a life of its own while you are writing. It's important that you let the story go where it needs to go. Think of your outline as one possibility. As you write, other avenues may suggest themselves. Follow those avenues. You will be surprised how often they will make the story better.
Put your story away for a couple of days after you've written it. It's easy to like what you've written in the heat of the moment. It's also easy to overlook holes in the plot. A couple of days away from it will allow you to look at it with fresh eyes. The best story typically comes in the rewriting phase.