Do you plan to write a short story, a novel or a poem? Each one will require a plot line which consists of a beginning, a middle and an end.
It sounds so simple, yet it can become terribly difficult.
Your beginning is an introduction. If you are planning a novel this is the part of the book where you introduce both the characters and the catalyst for the middle of your book. The catalyst is the event around which you will plan your plot. Too many characters may overwhelm you and the reader. A short story can have only one character. A novel may also have only one character if you happen to be a very good author. On your 3 x 5 cards or on your computer, keep a list of your characters. The list should include the name, age, occupation and description of each character. A reader will catch it if you describe Susan as a brunette with blue eyes and later refer to her brown eyes. Do not rely on memory. In a mystery, the catalyst may be the murder of one of the characters. In a romance the catalyst may be the moment two people meet and feel a connection. What you choose as the catalyst must carry through the beginning, middle and end.
The middle of the story is where you fill in the missing pieces. This should be outlined on your 3x5 cards. For instance, if the catalyst is a murder, you may develop the character of the murderer, and lay out the rivalries and conflicts between the characters. There will always be more than one to keep the reader guessing who is the real murderer.
The closing or end of the story ties everything together and reveals at the very end who committed the murder. You need to research every detail you choose to use. For instance, if the novel is historical, you will need to know the style of clothing, hair styles, types of architecture, and modes of transportation for the era. You need to research the city or country in which your plot occurs. Even in writing fantasy, you will need to be somewhat believable in your description.
Preparation is as important to a good story as the writing itself.