Scriptwriting for stage or screen is a very D.I.Y. sort of thing, ideally suited to introverts. Indeed, if you possess the requisite anti-social leanings, meaning you look at your shoes while talking to other people, then you can sit all alone in your garret writing to your heart’s content about the problems facing mankind, and you – until Doomsday. Actually some writers think Doomsday is right here and now, because it is so hard to get your precious gems of literary or filmic art appreciated. That is true! Just having your work actually put onstage or accepted by a film-making company requires the most incredible level of group effort and social interaction from a cast of thousands, well dozens at least, that you actually need to be an extrovert to pull it off. An extrovert is someone who looks at other people’s shoes while they are talking to them.
We can discuss this another time – how to get your work performed, that is.
But of course your work is far more artistically pure and impassioned if you suffer for it, preferably by starving half to death in the meantime. So suffer on, you’ll enjoy it. Oh I forgot to mention that writing is also for masochists. (Look it up).
Now, if you are not too discouraged already then we may as well proceed to the basic technique of scriptwriting.
This is what they will probably tell you in any scriptwriting course you may sign up for.
Or else, you got it from this Blog for free!

THE RULES OF SCRIPTWRITING:

Know What You Write, Write What You Know:

Entertainment is NOT the sole purpose of entertainment, there are other aspects as well, such as, uh, Education. Pssst! This is a secret; some folks will turn off if they find out they are supposed to be learning something, whereas others, like kids for instance will claim it is educational if it’s something they’re not supposed to be watching! Anyhow let me assure you as far as the rest of us go, that the audience may soon lose interest if they feel the writer does not know what he/she is talking about.
We all (mostly) love to learn something new.
That’s why your work needs to ‘ring true’.
Even Fantasy Fiction needs some degree of internal consistency – or logic.
Do your Research - Personal Experience is often the best kind of research.
(However, avoid casting all characters in your own mould, of course!)

Show Don’t Tell:

The difference between Drama (Tragedy / Comedy) on the one hand and Prose writing on the other, is this: In Drama we SHOW the audience by Action or dialogue, whereas in Prose writing we TELL or describe events to the reader. 
Nevertheless the NARRATOR– is a device used in Drama to TELL, just as in prose.
Now, the narrator can be used very effectively in a play or film, don’t get me wrong, it is just that narration is used sparingly in drama - and most usually, well, not at all.
Similarly; One of the fun things about Drama is how we may ‘show’ exactly the opposite to what we ‘tell’, for instance an actor describing his peaceful intentions while loading his gun.
So “actions talk louder than descriptive words” in drama, whereas in prose even the silent musings of the characters’ mind or soul are described in detail by the writer. This is not to denigrate the poem or novel where far more subtlety may be conveyed; it is just meant to show the difference between drama and prose.

Conflict:

“The Play Starts When The Conflict Starts, The Play Ends When The Conflict Ends”.
Conflict is where any two (or more) opposing forces meet.
It may be ‘man against man (or woman)’ OR ‘man against mountain’ OR ‘mountain against giant tsunami’ OR any other combination of the Animal, Vegetable or Mineral Kingdoms that you can think of!
Also conflict may involve, and usually does, juxtaposition of differing IDEAS.
The important thing to remember is that Conflict is the very soul of ALL Drama.
Cut the long preambles or postscripts; when the conflict is resolved, so is the play.

Larger Than Life:

We have already discussed how ‘truth’ is a necessary component in any creative writing  in order for it to have value, also that the writer’s intention may be un-stated and left for the audience to work out for themselves. Likewise we often employ irony or humour recognizing the well worn Shakespearean adage: “many a true word is spoken in jest”.
Having said all that, nevertheless the audience understands that for economy sake, the play must be streamlined, characters cut or merged, events simplified and various other departures from reality employed such as symbolism, time-warp, political correctness etc.  This is all lumped together and called “larger than life’.
In short, there has to be a trade-off between the story and a practical presentation of it.
Achieving such a balance is where the playwright’s tradecraft comes into play, as it were.
Note. Alternately it may be smaller than life, eg. “Snow White and the Seven Dwarfs” - just NOT life-size.
But wait a minute! Doesn’t all this amount to a watering down of the concept of ‘reality’?
Yes, certainly we have blown out of the water any idea of technical accuracy in our work.
The answer is that we call what we are doing, or what we must do, not a scam but rather; “Artistic Integrity”
… that gets us out of it, now moving on …

Structure Of The Play:

A Beginning A Middle and An End.
While sounding obvious, nevertheless plot development requires some changes in tempo, action and storyline in order to remain engaging. Such are generally announced by Scene changes or different Acts - in the case of the longer play. (This writer definitely suggests starting with Short Play OR One Act scripts, as they have more chance of being put on).

Various dramatic devices are employed to tell a story.
The standard Movie formula usually involves a shift in action at page 27 (the 27th minute)
Other formulaic requirements depend on the genre of the production but always adhere to the following pattern:

Climax:

The Action builds to a climax – actually there are TWO Climaxes near the end – a main climax followed shortly by a lesser climax, which is in turn followed by the Resolution.
Whilst normally tying up all the loose ends, occasionally the resolution may NOT resolve  but rather, include a ‘to be continued’ theme, as in Serials OR Series. This is similar to: -

The Plant:

For instance, during the 1st. scene someone picks up a hand grenade from the mantelpiece and comments about this souvenir from the war probably being ‘live’, then puts it back.
Nothing happens yet, this is the “plant”. However at the end of the play, someone goes berserk, grabs the hand grenade and threatens to blow everyone up! Now, if it had NOT been mentioned earlier then we would all say “where did that come from?” On the other hand, if the hand grenade is mentioned at the start then never referred to again, then we would say “what did the hand grenade have to do with it”?
From this we learn not only about the “plant” but also about “economy” in drama;
in other words “use it or lose it”. The play must be stripped down to bare essentials.
As stated earlier, the audience understand this.

The Twist:

Well-known, and always occurring near the end – we expect the unexpected.

Character is Plot:

A philosophical observation employed in history and daily life, for instance:
“Would WWII have happened without Adolf Hitler”?
OR “could your play have happened without this character”?

Proxy Experience – OR Acting Out:

Now we are really getting philosophical!
From observation I have come to the conclusion that a large-ish proportion of popular entertainment; from the hero legends of antiquity to the screen idols of the present day is mostly about escape or fantasy or vicariously acting out that which we are forbidden by law or social convention from attempting ourselves.
For example; what will happen if we do high speed car crashes, explosions or massacres?
It is too awful to contemplate!  But we can watch it at the movies.

Emotion:

However many different styles of plays and movies there are – we call them “Genres” 
Emotion is the driving force – the whole range of our emotions is the subject matter.
“Ideas” probably run a close second, but these ideas are explored in terms of emotions.
For example:

Good Versus Evil:

With the possible exception of golf and tennis, the entire world’s entertainment has been essentially hijacked by this awesome theme, and even in those innocuous sporting events the media go searching for captivating instances of human frailty.
Why?
Without doubt the nature of “Good and Evil” is the most gripping subject known to Man!
It forms the core subject matter for probably every script ever written in history, from the most weighty Classics through excruciatingly flippant Comedies, down to those animated cartoons which won’t leave in peace  the most minor of our flaws and peccadillo’s but rather parody in animal or robotic form nothing less than the ridiculousness of the human condition.
Nothing has changed. Art provides a stern commentary upon US. The most innocuous “Chick Flick” has a protagonist – or a pair of them usually – and an antagonist of course.
Good and Evil both prevail.

Anyhow, let’s explore some of the Genres;

Tragedy Or Comedy?

The Ancient Greeks are credited with inventing the Dramatic art form. We are familiar with the well known symbols of laughing and crying drama masks employed by Greek actors in their Classical productions which recognized only two forms, Comic OR Tragic.

Comedy:

Always has a happy ending.
Also no-one is ever seriously hurt, for example no matter what height the roadrunner falls from he emerges essentially unscathed. The same applies to car wrecks and explosions.
Comedy is optimistic.

Tragedy:

The essence of Greek tragedy involves an heroic character who possesses ONE fatal flaw which, despite all his other notable virtues, must inevitably bring him undone in the end.
For example, Achilles’ heel is his weak spot. Nowadays this image has come to represent some weakness in any one of us that may bring about, like Achilles, our personal failure.
The idea of unalterable fate is at the core of Greek tragedy
Tragedy is pessimistic.

Modern Genre:

A Multiplication of various Dramatic forms has taken place, some of them hybrids of the original Comic and Tragic traditions. For instance; “Action Adventure” and “Martial Arts” movies may be considered comedy because the hero invariably achieves a “happy ending” and gets the girl etc. However lots of other characters do get seriously hurt (or killed) – unlike true comedy.

“Sci-fi” – is a melting pot of everything from anything.
Horror Flicks, Vampire movies, more emotion – fear and laughter.

Then there is “Musical Comedy” which is a hybrid of Drama and Opera – although Greek Drama had the Chorus as well.
Children’s theatre and Movies derive from Pantomimes and Medieval “Punch and Judy” puppet shows and such.
Other sources of modern theatre and movies include:
Medieval Church Music, Oratorios, Morality Plays,
Circus and Sporting Entertainments, Jousting fairs,
Storytelling by travelling troubadours, poets and bards.
It all gets recycled continuously. Total Fantasy is all the go more than ever before.
Pick your genre.

Write For the Stage Not the Page:

This means your work has to work onstage!
It may, and usually does require “work-shopping”. That means you have to invite some
of your friends over to sit around and read it for you and then to criticize it afterwards.
The nearest equivalent to that is allowing them to torture, make fun of and humiliate your baby.
But it is worth it. Do it.
Afterwards you have to give them something to eat and drink (allowing a really stiff drink for yourself), then after a good weep, you start the re-write.
Good luck!

Admission:

All the best material in this article was borrowed from John Pooley – an excellent scriptwriting teacher who taught me most of what I know.
The remainder I deduced somehow from good and bad experiences.