What is the main drive of your campaign?
What are the six most important things you want your players to understand about the world and the campaign?
Who or what are the three major drivers in this campaign? Often these are villains. You don't want to share this with your players. Instead, create a villain card for each villain. Add a major goal for each villain and three sub-goals that take them to that goal.
What are the specifics of character creation for this world? What are the character building limits in this world? What house rules are in play?
Who are the patrons and factions the characters can be a part of? What brings the characters together to adventure in this campaign?
Discuss what safety tools you and your players are comfortable using during this campaign. Discuss any sensitive topics to be avoided. Consult this Consent in Gaming guide for details.