So how do you know?
The short answer is, you just know.
Which, I know, sounds glib, frustrating and unhelpful.
The medium length answer is, when you’re work starts selling or people start telling you they like what you write. But there are a couple of things wrong with this idea. One, we all know many, many writers who aren’t very good but are incredibly successful, and two, it means relying on other people to identify what’s good. Most people can identify what’s popular or trendy very easily, but not necessarily what’s good. Then again, a lot of what gets labeled as good writing just isn’t (oh, do I have a list of names for that one!).
Good writing and financial success don’t always go together. Sometimes, the best writers of a generation don’t get published because their work is too different, or they don’t find a wide audience because their work doesn’t resonate yet. Sometimes, the audience needs to learn how to read the work (the best example of something like this comes from music. When Stravinsky debuted his masterpiece, The Rite of Spring, with its discordant notes and chaotic rhythms, the audience rioted. A year later, when it was performed again, the audience loved it. In the intervening year, they had learned how to listen to the music and hear it as music rather than cacophony).
So how do you know if your work is good?
Here’s the long answer: you practice, practice, practice. You read, you write, you read what you’ve written, you read what other people have written, and you read some more. You take classes by people who know more than you do and you try the things they talk about. You listen to what they say about your writing. And you write, and write, and write. And you get honest with yourself about how close the writing comes to what you want. I mean, drop dead, no shit, honest. None of that, “it’s close enough” BS. I’m talking about pedal-to-the-metal honest with yourself about what you’ve written.
There are a few writers, an incredibly small number of writers, who are so talented everyone knows they’re good from the get-go. The funny thing is, though, the writers are usually the last to know. They usually have a teacher or someone along the way who tells them how good they are and then helps them get better.
I got my undergrad degree in creative writing. I went to school with a lot of talented writers and yet, I’m the only one still writing. Am I that much better than them? No. I just haven’t given up yet. I took a lot of classes and workshops and read voraciously about the craft of writing (my writing bookcase rivals that of any bookstore or library) and, when I wasn't finding anything new, I went to grad school and got my MFA. The professor who told me my novel is good told a class that there were many talented writers in the class and there were many who weren’t as gifted but who worked hard on their craft, and the ones who worked hard would probably find success more easily than those with sheer talent on their side. Talent only gets you so far. Then you need to work.
What the working gives you, what all that practice and reading gives you, is the ability to know when you get the words right. You may not know why the words are right, but you start to get a feel for it. You know it. And it’s not the hopeful knowing, the longing wish that it’s right, it’s the moment when you get it right and you don’t care if a single other person on the face of the planet ever agrees with you because you’ve said EXACTLY what you wanted to say in EXACTLY the way you wanted to say it. You can’t fake that moment.
You just know.