Tips for Session Planning?

Hello! I'm a new DM who's currently planning a campaign with a group of friends!

(Just to note I have never DMed before. I've had some experience with DND but its very minimal. I've done 2 sessions as a player max before our campaign kind of broke apart due to schedule issues)

I'm planning notes for DND stuff in my notebook to prepare for our session. I currently have some basic things in there like basic world stuff, some rules, and other things. Is there anything specific that's a must have in my notes?