And now, in the homestretch, let me put on the brakes and give you some sage words. Words that I've come to appreciate after my experiences, and words which I didn't fully get until I lived them:
Making mistakes is not the problem: NOT learning from them is.
You're a new screenwriter, still finding your voice and what genres you are genuinely the best at. You'll make mistakes, no matter what you do. You'll write flaccid dialogue or wonky structure or poor characters. You'll make something too big for your level, both in industry terms and your own writing experience, and you'll make something too small, that has no appeal or story engine.
And you know what? It's okay.
No really, not setting you up: it's alright to make mistakes and write crap. It's not the end of the world if your first or second script suck the big one and make no sense: you're still learning. Getting to the end of a draft is a victory: do you know how many people can't even make it to page 30? Being able to do a complete rewrite is another victory: how many people stupidly think their first draft is perfect?
However, these small victories will mean nothing if you can't exercise, arguably, the most important tool in your writing arsenal: critical thinking. Learn and understand why something isn't working, and then develop ways to fix it. How can you make this line of bad dialogue sing? How can you make this boring character interesting? How can you make this moment of tension even bigger? Trial and error, that's how. It's slow, it's tedious, but worth every second.
You know that else? Projects can collapse on you: talent will back out, money gets lost or overspent, scripts will not work out etc.. Just this past year, I had a fantasy feature and a sci-fi short die on me. Last year, staffing on two webseries. You take it in, have a deep breath and, if you really want this career, soldier on. Again, learn from it.
You know the one mistake that is genuinely inexcusable? Being an arrogant tit.
I've remarked on it before, but I'll say it once more for those suffering from selective reading (a common malady on the internet):
If you're a pain, no one will work with you.
You're a no-name at the bottom of the heap, untested and unproven: you DON'T get to act all big and tough, telling people more experienced than you that they're wrong. If you can't be bothered to write a decent logline, or a comprehensible synopsis, or even just being able to state what your project's about, why oh why, do you think ANYONE will treat you with respect?
In what fairytale la-la-land do you think you can get thousands, nay, millions, of pounds/dollars invested in you with poorly spelled, generic, bland and whiney proposals and scripts? Really, I'd love to know: it'd make my life a whole lot easier.
Just look at this joker from a Facebook screenwriting group (he's asking for an actor, but I've seen countless wannabe writers do the same thing). When I tried to point out that his presentation was uninformative and unprofessional, look what he wrote in response (top comment):
I am sick and tired of seeing lazy pitches like this on FB, as well as forums like reddit, Stage32 and Amazon Studios. I am fed up with this missplaced sense of entitlement and bad attitude towards your peers. If you think, even for one second, that the industry owes YOU something, you're out of your mind. If
you think you can just waltz onto a forum or Facebook group and DEMAND
things, like exec emails or producers' cash, you're also nuts. And if,
and this is arguably the worst yet, get snippy and defensive when people
try to HELP you, then please, do society a favour and check yourself
Harsh? Yes, but necessary: it's such a basic mistake that, by avoiding, you already put yourself light years ahead of the competition, just like with basic proof reading and saying 'thank you'. Everything about being a screenwriter is in the details. Take it from Joe Carnahan:
And with that, we've arrived at the end of our strange little journey. I
really hope you found this series of use and will, at least, be spared a
few headaches. Like I said before, I can't give you miracle cures or
cheats: I can only tell you what I've learnt and am still learning. I'm
still a student of the medium, and I'm well aware that there will be ups
and downs along the way. There will be producers I don't impress, or
scripts I can't finish, or series I can't get involved with, but you
know what? I'll still keep going, because I know I've got the tenacity
and hunger to want it that bad, and to work that hard.