Substack is designed to help writers publish their work and to help readers support those writers whose work they enjoy. The most obvious way to support a writer is to commit to a paid subscription (something which every writer will appreciate), but there are many other ways you can support a writer that are free:
Liking a post
Commenting on a post
Restacking a post, preferably with a comment about why you liked it
Recommending the author’s Substack through the Recommendations feature
Joining that Substack’s chat and contributing to the conversation there
Writing directly to the author to say that you appreciated what they wrote
Sharing the post in other social media or email
Recommending the writer’s Substack orally to people you know
If you also write on Substack, mentioning the post in one of your own
If you also write on Substack, suggesting a collaboration of some kind
If you ever meet the author face-to-face, mentioning something they wrote that moved you
Coming back to read the next post, and the one after that, and the one after that
I think I speak for pretty much all writers on Substack when I say that all of these gestures are tremendously appreciated. Would that Wallace Stevens were still around and on Substack!
I have thought of another way to support a writer you like, which is so obvious I overlooked it: buy their books!