We've had a ton of new users in the past week+, so I'm gonna break tradition and do one of these a bit early:
1) Your instance is probably run by someone as a hobby. Be kind. Be helpful. Contribute if you can.
2) Always use alt text on images. I know, it takes time. But it's one of the things we do here to support vision-impaired users, because they deserve to browse funny cat pics too
3) Use content warnings, and not just for "offensive" content. If your post could generate strong emotions (heavy politics, common PTSD triggers, tragedy, etc) let people keep it hidden for their own mental health