Show HN is a way to share something that you've made on Hacker News.
What to Submit
Show HN is for something you've made that other people can play with. HN users can try it out, give you feedback, and ask questions in the thread.
A Show HN needn't be complicated or look slick. The community is comfortable with work that's at an early stage.
If your work isn't ready for people to try out yet, please don't do a Show HN. Once it's ready, come back and do it then.
Blog posts, sign-up pages, and fundraisers can't be tried out, so they can't be Show HNs.
New features and upgrades ("Foo 1.3.1 is out") generally aren't substantive enough to be Show HNs. A major overhaul is probably ok.
Be respectful. Anyone sharing work is making a contribution, however modest.
Ask questions out of curiosity. Don't cross-examine.
Instead of "you're doing it wrong", suggest alternatives. When someone is learning, help them learn more.
When something isn't good, you needn't pretend that it is. But don't be gratuitously negative.