A lot of new writers believe that having a "voice" is somehow accidental. That other writers somehow are blessed with it, as a gift from The Writing Fairies or maybe THE MUSE OF SHANE BLACK/QUENTIN TARANTINO/SYD FIELD/ROBERT MCKEE/LINDA SEGER * (*insert "cool" screenwriter or script guru here).
Newsflash. If your voice is YOU, then only YOU can discover and develop your voice. No amount of reading scriptwriting books or even scripts will make you pinpoint that certain "something" that only YOU can give your scripts and absolutely no one else. Craft is craft and whilst it's certainly advisable to be as polished as one can, especially in the spec market, you're an individual. Don't sell your voice short or ignore it altogether; chances are you won't "stand out" if you do, and "standing out" is a very good idea in this biz; even if people hate your material, they'll remember YOU.
Having a voice is not something that "takes time to show" through a body of work in my opinion, it's a conscious effort, a lifestyle choice when writing, if you like. I have long term clients and colleagues with very strong voices; even without a title page, I can guess who is who, not because I've read so MUCH of their work, but because every single script they have written, regardless of genre or subject, regardless even of of the stage the draft is at development, first, fifth or fifteenth, has one thing in common - their voice.
I believe it's possible to develop your voice from the very first script you write. I blew off the dust from this rejection letter from an agent regarding a script I wrote when I was just 19. I hadn't gone on a scriptwriting course at this point, I didn't have the internet at home and I had read one book, the legendary Teach Yourself Screenwriting by Raymond Frensham, so it's pretty fair to say that the script was a bit of a mess. However, the agent in question was really kind and gave me two pages of feedback, of which this is an excerpt regarding my "voice":
Though for the most part I must confess that I didn't really understand your story, I really liked your style. You have good imagery in there and a vital way of writing that really communicates something - even if I wasn't exactly sure what that "something" was!
She went on to reccommend Bournemouth and I applied, got in and went the following academic year: the rest is history, showing rejections are not always the end of the road.
But anyway. I had "something" apparently; no one knew what that was yet, least of all me. I was a little terror-struck at first: what could I do about it? Writers were just writers... Weren't they?
No. I believe that old adage: creativity is 1% inspiration and 99% perspiration. Those Writers who "make it" in my view know they have endless rewrites and copious learning on the job: they also know they must have a voice and know how to go about developing theirs. So this is how I believe you do it...
1. Copy. When I was a small child, I wanted to be a novelist. Whilst under ten, I spent a lot of time reading myths and legends and Grimm fairy tales, but also more innocent stuff like Enid Blyton. However, by double figures I had graduated to the creepier tales of Robert Westall (just thinking about The Wind Eye makes me shudder, even now) and Robert Swindell (Daz 4 Zoe, anyone? What a book!). When I hit 12, with a reading age of 18+, I had exhausted the children's section at my local library and started on the adults' section. Much to the chagrin of my parents, I developed a liking for Dean Koontz, Stephen King, Shaun Hutson and Clive Barker. Like most kids, I believed that somehow stuff on TV was "accidental" - that you left a camera running and stuff just "happened". So when my mother brought me a book from a charity shop - the aforementioned Teach Yourself Screenwriting - suddenly, a whole new avenue opened up for me and I started to write short scripts. They were all awful and just about every single one had vampires and warlocks and supernatural stuff in, just like my novelist heroes, but this copying between about 14 and 21 is the major contributor to how I write now.
2. Write what you know. This does NOT mean if you're a nurse, write just about being a nurse or whatever. Absolutely not. If everyone wrote only what they had actually ever done, how boring would that be? The thriller and horror genres would be a lot smaller and sci-fi most likely non-existent - how many writers have gone into space? I can just imagine telling "Write what you know" in this regard to a writer like HG Wells: "You can't write a book about a Time Machine you fool, you haven't invented one! And by the way, when did those Aliens invade Earth again and then die of the cold virus?" Eeek. So, instead, think of "write what you know" both metaphorically AND literally. You have actual experiences, yes, but you have opinions, morals, politics, etc too. Which ones do you want or feel you should reflect in your work? Why? Then there are all your influences to consider, too. By now you should be beyond copying and drawing inspiration instead from aspects of books, other films, people or in my case in particular, music. This is also leads into number 3.
3. Re/presentation. No, this isn't anything to do with format or getting an agent; it's about RE-presenting who YOU are through your work, thinking about what concerns and issues you have and how you want to disseminate this information through your script/s. Though I have written vastly different genres - family, horror, supernatural thriller, psychological drama - all share one thing in common: the theme of responsibility. In reality, people who live in denial or shirk their responsibilities, especially absent parents, really gets my goat. It's no accident then that this has made its way, covertly and overtly, into my scripts. I have a big interest in both psychology and philosophy - yet again, these two things have made their way into my drafts, some more obvious than others, as have literary allusions, given my background in English teaching.
4. Arena. Arena is such an under-used tool in reflecting Number 3. One of my scripts has a twisted Alice in Wonderland motif running right through it from beginning to end; some Readers have picked up on it, some haven't, but that does not mean you shouldn't use these devices in developing your voice.
5. Know your message, thus know your story. So many new writers want to write a series of images that looks cool rather than an actual story. I did when I first started. I had a mess of stuff in my brain that just came spewing out in a stream of consciousness. The key here is in getting to the root of what you're saying and why. If your story is a tree, then your message is the acorn it grows from. If you don't know what your message is, then your story may not make sense and your voice will go unheard.