What's your quick, go-to writing advice?
Write.
Besides knowing the language you are writing in and how to write a story and all that, that's basically it.
Anything else is largely a search for validation rather than a solicitation for actual advice.
There's also the danger of buying into advice that's not conducive to your growth as a writer.
It can also feed insecurities.
Many moons ago, when I was an eager future writer still in high school, I tried to get into a writing course. It was a mail order writing course. I don't remember which one off-hand, but it seemed legit. So, I sent for more information and such, and once they found out my age, they wanted to enroll me into the "young writers" course, not the regular course. I wanted to be taken seriously as a writer, not be treated like a kid. So, I found that somewhat offensive, trying to treat me differently not based on the quality of my writing but based on my age. Then, when I didn't sign up, they started sending letters addressed to "the parents of" which was even more infuriating.
And then I read advice somewhere that you shouldn't even try to be a writer until you've lived your life. Before you write, you should get married, have kids, get divorced, etc., etc., basically experience everything before you ever put a pen to paper (this was the "old days," you know?).
I dismissed it all, of course. I mean, did any scifi or fantasy writers actually experience traveling to distant worlds or fighting trolls? (Before the Internet, of course.)
But, somewhere, it probably stuck in the back of my mind. I had stories I liked and I set them aside because I thought I couldn't do them justice until I became a better writer.
Well, how does one become a better writer without writing?
So, it all comes down to just write.
How much farther along would I be if I had written consistently until putting stuff off until I became a better writer? How much faster could I have become a better writer if I had been more consistent with doing the actual writing part?
Granted, I got sidetracked with other things I really wanted to do, such as make horror films. Never got far, largely because I also wanted to do a magazine and after I launched my first issue, I found I needed to change the name and while contemplating new names, I discovered the early days of the Internet and got well sidetracked.
Bottom line is, again, write.
On top of that, one writer will advise one thing and another will advise something else. And if the advice of the writer(s) you admire is advice that really doesn't work for you, you may feel like less of a writer because you can't live up to the standards of "real" writers. Or whatever.
So just write.
Who cares what Stephen King says? Who cares what J.K. Rowling says? Who cares what any other writing clown says? Forget them. Don't take any writers advice as gospel truth because it isn't, except this: write.
Find your own voice.
Find what works for you.
Tell the story you want to tell.
The only way to do that is to write.
So write.
Plot or don't plot. Figure out what works for you and write.
Dictation or keyboard. Figure out what works for you and write.
Paper and keyboard. Seriously, type it on a computer so you don't need to retype.
But, anyway, just write.
Read, sure.
Learn the craft, sure.
Know the language, sure.
But write.
It doesn't matter if you write fifty words a day or five thousand words a day, just write.
Does a particular scene work or not? You can play it over and over in your head but the only way to know for sure is to write.
Which word choice is better? Write it down and figure it out.
First person? Third person? Past? Present? Future? Just write the thing.
Nothing matters if you don't write it down. So write it down.
It all comes down to one word: Write.
