These resources on promoting your group and events from the EA Groups Resource Centre might help! https://resources.eagroups.org/running-a-group/promotion-advertising
Very old guide, maybe a tiny bit helpful: How to Run a Successful Less Wrong Meetup Group.
A necessary (but not sufficient) condition is that the people who want to attend meetups can find out when and where they are happening. You might think this is obvious, but my local group requires a login in order to view its "public calendar".
I'm not sure I fully understand what you're asking; are you asking:
I'm asking the first question.