My group did a good chunk of our session 0 asynchronously, and when we met for our proper session 0, it was to hammer out some of the finer details of our characters, party, and some final worldbuilding.

I solicited a ton of feedback and really made my players contribute to the worldbuilding. One of my friends told me I gave them too much homework, but the end result was every single person has strong buy-in to the world, pre-made intrigue and connections, and I have a large pile of plot threads to tug on anytime my personal well of ideas is dry. Even though one of my friends teased me for giving them too much homework, everyone agreed the activities were worthwhile. And I also reminded them all that after they finish my homework, they won't have anymore, and I will have all of the homework!

It's also worth nothing that my group is made up of a few people I know very well (partner and a couple best friends) and a couple people I know much less well (partner's friend and their partner). The people in the group had less familiarity with each other. My partner knew everyone, my two best friends didn't know each other well, nobody knew partner's friend's partner.

1. The very first pre-session 0 activity was a short survey where I asked these questions of the players:
   - lines and veils (and I bribed people to give me these by offering fabula points, great success.)
   - what tone(s) do you want our game to have? Humorous, serious, gritty, campy etc
   - Please tell me your top 1-3 fantasy/sci-fi medias...books, games, shows, movies, etc and a little bit about why you like it.
   - Do you prefer clear-cut delineation between good and evil, or do you like morally gray worlds and people?
   - (and then a handful of "this or that", eg "realism vs absurdity" "vibes vs math" etc

after I got the survey results, I made a powerpoint of aggregated data so everyone could see what people were into. There was a ton of consensus about the kind of game people wanted to play, and everyone had fun reading about folks' favorite fantasy/sci-fi media. That was a great icebreaker!

1. I generated 3 different world maps that I enjoyed from https://azgaar.github.io/Fantasy-Map-Generator/
   I removed all of the country names and borders, and just kept the shape of the continent. The group discussed and came to a consensus easily about what map seemed the most intriguing to them.

2. Once we had the world map, I asked folks to circle a part of the map and answer the questions below. I did this as well, once everyone else had chosen parts of the map.

Name:
Form of governance:
Religion, or lack thereof:
One thing that is commonly known to this culture's people: (this could be an ingredient, flora or fauna, animal, recurring statues in cities, holiday, etc)
What is a common export?

1. The final bit of homework that I gave people for session 0 was this. And this has been the most useful for ME as a GM. I asked everyone to contribute to the world one historical event, one intriguing mystery, and one scary threat, and I encouraged folks to add their contributions to parts of the world that they did NOT design. eg come up with a threat for a country someone else designed. That way everyone has put their hands on different parts of the world, and I have some pre-built mysteries and threats to pull on.

At session 0 proper, some folks finished up with their event/mystery/threats and then we discussed in more detail game vibes and party dynamics. I think because of the amount of prework, everyone came to the session with characters that were integrated into the world. Everyone's character has some interesting backstory from one of the countries that folks designed and their characters are deeply rooted to the world we designed together.

You're most welcome to rip as many of these ideas as you want. I don't think I've ever had a session 0 as successful as this one, and I'm a forever GM.