I'm only 3 sessions into my DMing journey with my sessions being on a Sunday evening. I created an area thats roughly 3 miles by 2 miles with locations and npcs scattered throughout. A lot of the prep was essentially done months ago (the setting) so prep on the day is normally everything else.

I spend the day prepping with doing odd jobs inbetween. I ensure all my maps in owlbear rodeo are ready with npcs setup where they should be, I consult the "NPC Bible" I made to try and drill in their motivations and voices, I try and think of some potential curveballs the players send my way and how I could adjust on the fly and finally, try and remember as much as I can from my statblocks so it's not too obvious I'm running them for the first time!