Read or see some of the great theatrical works such as "Our Town," "Death of a Salesman" and "The Fantastics." Read about what makes for a great script. Realistic characters, dramatic dialogue and a complicated central conflict are all core pieces of a strong script.
Write your script. Don't try to make it perfect. Expect that your script will change. The way a script reads on the page is not always an indication of how it will seem on stage.
Gather friends and family for a living room reading of your script. This is typically a simple read-through of the dialogue. Only one rehearsal is necessary before the reading. Take notes and listen to the actors' feedback about character development and dialogue.
Re-write the script based on the notes. This is a critical step in seeing a fproduction of your script on stage. Edit the script to make the story clear but not obvious to an audience. Theater-goers do not like to be spoon-fed a story. Equally frustrating is a play that is confusing or vague.
Get the play produced. This is the most critical part of the process to putting your story on stage. You can front the money to hire the actors, pay a director, rent the theater, pay production costs and market the show. You can also simply submit your script to various theaters and theater companies and hope one of them produces the script.