There are a few steps to becoming a screenwriter that cannot be skipped. No doubt you can point to someone that wrote one script and sold it for a million dollars, but that’s not you. Those stories are like the guy who shot himself in the head and removed the tumour that was killing him. That is not a plan, it is a miracle.
You must learn screenwriting (and continue).
The best way to learn screenwriting is to read screenplays. By reading screenplays you will learn how to pace a story, how to format your script and how to use things like action, description and dialogue.
Here is a great place to find scripts. Simple Scripts.
Start writing a screenplay.
You should try writing a short screenplay first. Mostly because you will make all your mistakes in this script. You can rewrite it and play with all aspects of writing. It is better to cut your teeth on a short rather than slogging through a full length feature. It is easier to fix five pages of dialogue than a hundred pages of dialogue.
Make your movie.
You want to write a movie that can sell? You need to know how what you write impacts on a production. This will also teach you to write to a budget. So rather than have a spaceship land and someone walk out of it to say something. You will write them having the conversation in a room. It is funny how people learn to write to a budget when it is their own money.
If you don’t want to make a movie. Okay. You should stop reading this article. You should go and buy a “how to write a screenplay” book. Follow all the formulas and templates and lament why you can’t sell a screenplay. Or you can make a short film and grow more as a writer than you ever imagined. It is up to you.
Write more screenplays.
You will not believe this. But you will come to believe it with experience. Your first screenplay isn’t very good. It doesn’t have the gravity of your future work. It doesn’t have the emotional depth of your future work. It doesn’t have real and engaging characters like your future work. So put it to one side and write more screenplays.
Think of painters. They paint hundreds of paintings before they even think of displaying their work. Only us screenwriters are arrogant enough to think our first completed work should be sold to a studio and appear in a cinema. Don’t be naive, you will need to write a lot of scripts to get good enough to be considered a writer.
Still keep reading screenplays and making short films.
When it is time, you’ll know.
There will be a moment when you suddenly realise you didn’t know anything previously. You can see the craft stretching off into the distance and you know that it is a lifelong journey. Congratulations, you are a writer. You are now able to assess your own work with some degree of accuracy. Find your best (least embarrassing) script and post it online for people to see. I would suggest scriptrevolution.com as a good place.
You will start to get people reading your work and you will get some comments. This is what you need to learn more about yourself as a writer.
So to recap.
Write a short.
Make a short.
Read more screenplays.
Write your first feature.
Hide your first feature.
Write more. (When you feel you are good).
Post some good work online.
I hope this helps. Most important is that this is a long and hard road. It is self employment mostly and you are never guaranteed success.
You only have one chance at a first impression. Make it a good one. Keep all the bad work with you and be super prepared for success when it comes. There is no queue jumping or short cuts. Just writing.