In addition to the ^^^How They Work^^^ which covers the criteria used to access the events, including eligibility, I would also suggest reading the post as well.
https://community.justinguitar.com/t/the-community-open-mic-events-category/2816
which also covers how the JGC OMs started and why.
And look out for the Call For Interest posts, which come out shortly after each “show” :
https://community.justinguitar.com/t/open-mic-011-call-for-interest/120335/73
Cheers
Toby
