The blank page can be very daunting.
You know when you've got an idea, but something stops you from getting it out of your head, and onto the page? It's usually fear. Fear that it will be crap.
One very successful trick I've found is to just, well, write it down. Blindingly obvious, right? That's what you're trying to do FFS. Stay with me here people.
There's something about the process of forming words and sentences in your head - even if they're utter drivel - then transferring them onto the page, that frees your mind of the blocks you previously had in there.
And while the first paragraph, your first page (or pages) will be rubbish - and be nothing like what you are trying to achieve, - the very fact you've decluttered your mind through the process of writing will help you get to the core of the idea faster.
This is particularly helpful for non-writers, or those just starting out. Just get it down. You're about to exercise your writing muscles. But muscles don't work at their full potential unless they're warmed up first. Skip the warm up and the whole workout could go to sh!t. You want to get from writing amateur to writing Arnie, right? So c'maaan! Doo eet!
Just start writing. Anything.
In fact, when I came to write this blog post, I looked in my Faster Ideas notebook and just saw the words 'Write It'. I was scared I wouldn't know what to write. So I just started. Writing. And here we are.