The basics of scriptwriting can be put into 5 steps as noted by celtx though these same steps are present in other sources .
Before any of these steps can instruct you on the basics of Scriptwriting ,you have to understand the nature of film itself , this is mostly achieved by just growing up watching movies and slowly learning the nature of them as a whole even to the point where we as viewers can even pick up on clichés or what a character will do next or maybe when there might be a plot twist.
This underlining understanding of cinema is necessary before trying to undergo how to learn how to create a script.
Step 1: The Logline and Character development.
A Logline is a one or two sentence interesting summary of the entire story. After that’s done you can start developing your characters , you have to find out what makes them, them , writing there personality’s and backstories is a good place to start. You also have to think of their goals , what are they aiming towards are there high stakes if they fail to meet that goal it could be that the character just didn’t get to the store on time to get there favourite snack or it could be the end of the world.
Step 2 : The Outline
An Outline is basiclly the structure of the story itself , this a point by point structure of where you want your story to go .This can be based on the cinematic sense in a three arc base story structure but this is not set in stone and something that has to be done as instructed by a piece of paper , their is a lot of room just improve and interpret that someone wishes too , though this base structure of story telling has lasted so long because its how people assume or expect stories to be told.
To achieve the basic structure a normal Screenplay or script is around 90 pages in length ,if you took that a face value all you’d need to do is put that into thirds leaving you with 30 pages for each act. Act 1 normally dictates that the introduction of characters and there motivation be present here as well as the inciting incident to give the story the push to get it going . Act 2 is sometimes the most exciting out of all the acts as it normally contains the obstacles that the characters have to face as well as the intensity of the event that rises to Act 3 . This is the climax of the entire story and after this everything slows down to its resolution .
Step 3: Writing a Treatment
These are in the simplests term a more detailed version of the outline . You should write your story out scene by scene and go indepth into the world and what you are trying to create . In sense this is a lot like a tradional manuscript . Exprimentation of what you want the characters to do is okay , for example exprimentation with diolog is completely fine and decribing settings devloping them is a good option at this point.
the length of this is entirly dependant on hwo long you want your story to be and the type of story you are trying to tell , though as a note this normally takes up about thirty pages in length
Step 4: Finally writing the script
This step is litrally just wrting it itself . Though important notes to remember are keep it in present tense and show your audience not tell them other than that there isn’t that much to this step other then just writing .
Step 5: Rewiting the script again and again
After writing it you maybe inclinded to think its a polished gem , its not this step is to just go over it again and again, look at it objectivly what you dont actaully need , rewrite it and just trim off the fat . Repeat .