Hi! Thanks so much for your question. I’ve been meaning to write a post like this, so thanks for giving me some motivation to finally write it. Ever since I began screenwriting, I’ve reached out to more experienced screenwriters for advice and it has paid off immensely. So kudos to you for taking the initiative!
This may be a little lengthy (sorry!).
I try to read all the time. Get your hand on as many scripts as possible and read. At the beginning, read really good scripts. Read film scripts that were nominated for Best Screenplay and pilot episodes of shows that are now on season 4 or further. Read scripts from your favorite TV shows and see how it differs from the final product.
While you read, absorb everything. How are characters introduced? What does the script do particularly well, and how? You can pick up on formatting just through reading scripts and paying attention. It’s also helpful to read books on screenwriting. One I suggest is “The 101 Habits of Highly Successful Screenwriters”. It covers a little bit of everything and is an easy read. I also read a lot of fiction and nonfiction. Reading for fun can be really nice.
I try to write a lot. I don’t believe in the golden rule of “write every day”. For non-professionals (aka. the majority of us with school/work/a life), the expectation to write every day can be a intimidating. However, the only way to become a screenwriter is by writing. So set a goal to write (and really focus, no Facebook, no texting, etc.) 4-5 days a week. That way, if you miss a day of writing, you won’t be sucked into a black hole.
I receive constant feedback. Find a writing partner who can comment on your script. I don’t mean “you need a comma here” comment. Those are just mechanical issues; I’m talking about the Big Picture. A partner that can recognize a weak character or plot, or that you need to delete the first 10 pages of your script.
Preferably you’ll want another (screen)writer, maybe one with a bit more experience to answer any questions. If you’re at uni, see if there’s a writing center. I met with the most fantastic MFA in Screenwriting student and worked with her every single week. This forced me to a) write often and b) write better. My skills improved drastically and my confidence also grew. It was during this time that I decided to apply to MFA Screenwriting programs.
I hope my response is satisfactory! If you have any questions (about screenwriting or anything!), I’m more than happy to try and answer them. @lifeascaty, @writerlyn, and @annerocious are wonderful screenwriters here on tumblr and are way more qualified to answer your question than I am. Best of luck to you and your screenwriting journey!
Thanks!