By learning to write a screenplay can enable one to make a career in the film industry sooner or later as there is big demand for new stories and writers. Also you can win a screenplay competition. But to write a screenplay one needs a strong idea and storyline around which the screenplay can be developed. The key ingredients of a screenplay are the plot, characters, and presentation. The plot needs to be original and the set of roles and characters need to be described in as much detail as possible. The screenplay media is a visual medium, more than the storyline the environment in which the story takes place has to be described in great detail.
So apart from the story telling ability the writer has to have a keen eye for describing the scenes in full. With Hollywood always looking for new genre of writers, submitting screenplays to various contests and agents is a good way to increase the probability of success.