Okay, so I don't think it's a huge secret that I'm a bit on the unconventional side when it comes to writing. I don't outline, I don't name characters until halfway through books, I switch up eye colors, etc. (BTW, all that gets fixed eventually. My first drafts are nightmares.)
Writing the beginning is no different. It's simple really. Don't write it first.
Now I don't necessarily write my beginning last, but I don't stress about writing it straight out of the gate either. Let me explain.
So I don't write in order. The first scene I wrote in POSSESSION shows up in the book on page 130. The second scene I wrote is the one before that one. And the third scene appears about page 45.
I don't worry about when I write the scenes. I worry about where they go in the story and how they fit with what else I've got. I worry about stitching them together with transitions. I worry about what needs to happen earlier in the book so that the scene I just wrote will make sense. And so I piece together my scenes, writing notes in between them for what needs to happen, and possible ideas for what could happen later.
I write what's in my head, and nothing more. Beginning, middle, end. Doesn't matter when it gets on the page, just that it does.
Unconventional, I know.
But I think there's something to be learned here. Beginnings do not have to be written first. Don't know your beginning? No problem. Write what you do know. You can work backward to the opening scene at any time.
When do you write your beginning? Are you able to write without having that opening scene down on paper?