Be it devising a screenplay for a short film, or planning the writing for a doc, vlog, etc., it does help to write within some kind of framework. Knowing the basic structure of most dramas will help you get started in thinking about the structure of the story before you begin the actual process of writing. Think of the following as your scriptwriting "game plan." Use the model of the 3 Act Play to guide you in constructing your story, and then your script will be a lot easier to complete.
As you write, it is important to keep your intended audience in mind. You will be answering the question: "who will be viewing my film?"
In a 3 Act Play:
There are the 4 main components of a story:
Events: an event or series of events that happen over a given period of time. The cause and effects of this series of events can be referred to as "the plot."
Setting: the location or series of locations where the events happen. You can almost think of the setting as the story's "world."
Characters: the different people in the story that perpetuate the events. Heroes and villains (protagonists and antagonists) are commonly found in stories.
Theme: the main idea or "philosophy" which guides the story and is most important for the writer to express. Man vs. Man. Man vs. Nature. Man vs. Machine. Love. Sacrifice. Good vs. Evil. These are common themes that can be found in even the simplest of stories.
When these components combined, and then placed into a structure (like this classic three act structure), a story can be more easily constructed.
The Classic "Three Act Play" Dramatic Structure
Introduces the characters, the location, and begins to intertwine events. Called Exposition.
Protagonist tries to resolve first conflict but problem gets even worse. Referred to as Rising Action.
Climax and Resolution of the story. Sometimes called Falling Action.
Inciting incident or "catalyst" occurs, often delivered by an antagonist (the bad guy).
The skills needed to defeat antagonist are not yet learned, protagonist is discouraged by monumental task.
Final confrontation takes place: Plot Point III.
Conflict is introduced to protagonist (the hero).
Antagonist throws obstacles in way of protagonist to prevent defeat.
Antagonist comes out strong, Protagonist takes on setbacks.
Dealing with conflict creates second more serious problem AKA Plot Point I.
New skills must be learned in order for self actualization to occur, changing the protagonist ever more, & steeling the hero's resolve in order to defeat the antagonist.
Powers learned help teach antagonist lesson about right versus wrong, but is it enough?
Plot Point I changes life of protagonist, reaches the point of no return.
The change the protagonist undergoes requires help from others, like a teacher or mentor, a love interest, or some other co-protagonist.
Conclusion: Is Antagonist is defeated? Or has Antagonist prevailed?
Introduces the dramatic question: the protagonist's call to action.
Protagonist finds a way to confront the antagonist, who cannot be defeated without a plan and the assistance of co-protagonists.
Victory is celebrated by winning side, loser is laid to rest.
Theme of the film is introduced: good vs. evil, courage & heroism, coming of age, love, death, power & corruption, individual vs. society, etc.
The final conflict is staged, which is Plot Point 2.
Resolution of subplots and a brief moment of calm AKA dénouement.
Introduction of Plot Point I ends Act I.
Introduction of Plot Point 2 ends Act II.
Plot Point III is resolved End Act III.
Knowing how this three act basic dramatic structure works, then creating individual scenes that make up each act (as some do, onto note cards) can really set you up for the next task; writing the script. You'd be surprised how working within a framework almost provides a recipe for creating a dramatic script. While the script doesn't write itself, you'll find it extremely helpful to build in your own guidelines for story. You can use popular screenwriting creation software to assist you. More info here.