Let's be clear: you don't have a lot of time to get the story going, develop it and produce a satisfying ending. So things must move along without much waffle or padding.
The first thing is to get off to a good start, and the way to do that is to pitch right in with some attention grabbing stuff.
A is for action.
Put a dollop of attention grabbing action into the very first sentence or paragraph. This doesn't have to be 'Raiders of the Lost Ark' from the word go, but can be your hero rushing to keep an important appointment, or it could be a heated argument, or maybe a near accident involving your hero. Get your reader engaged and they will stick with you.
B is for background.
The next thing is to give your reader some context for the tale you're about to unfold. Things like: Where is the action taking place? What is the name of your hero (which gives the reader his or her gender)? What circumstances led up to the opening paragraph? All these will fill in important background details to help the reader understand the story better. This is also a good place to give a teaser or signpost to what dire events may be about to happen. Such as "Ben fought hard to control his anger. He knew he was only seconds away from making the biggest mistake of his life."
D is for development.
Next we have to let the reader into what the problem is that the hero has to overcome. What is his challenge? What would the outcome be if he failed? Move the story forward with interaction between him and the antagonist (which may not be a person, but anything that is stopping him from getting his life back to normal). When other characters enter the story remember to 'show not tell'. That is to say bring in dialogue to show what is going on, together with emotion. Fear, love, insecurity, anguish. You name it.
C is for climax or conflict.
The is the part which the story has been building towards. The final countdown where the hero faces the challenge which will bring about success or failure. The climax is a conflict or a fight. A real physical one or a fight to overcome circumstances or emotions, or to save a loved one. Bring him through this (usually successfully) and then show your reader how the whole experience has changed him and made him a better person.
E is for ending.
Your hero has got his life and circumstances sorted, has fallen into the arms of his beloved, and all, thankfully, is now well. Your reader breathes a sigh of relief. But are there any loose ends to be tidied up? Do that here. Be succinct though. The story has been told, but your reader may worry if there are any unresolved threads left hanging.
This simple formula has stood the test of time and, whilst the actual plot is up to you, using it will give your readers a satisfying experience and leave them wanting more.