Get it tested before you launch
You only get one first impression on a launch site. Before you post anywhere big, have a few people use your app and fix what they find. A launch that breaks on sign-up wastes the attention you worked for.
Write a post people click
Lead with who it's for and the one problem it solves, add a screenshot or short video, and say what kind of feedback you want. Answer every comment, and turn the good ideas into your next version.