Hey! I have around ~15k GitHub stars and am generally known for nice READMEs. My 3 biggest tips are: 1. Show what you do (better yet: let the user use your software) 2. Show how you're better than competitors (feature comparison) 3. Network effect (thanking contribs, people, other projects etc)

I wrote much more deeply about this on my blog: https://skerritt.blog/make-popular-open-source-projects/