Nuclear war, zombie outbreaks, meteor strikes, economic collapse, alien invasion, no matter how it happens an apocalypse makes for a unique and engaging setting to run a campaign in, even for a jaded GM.
Here’s a few quick tips that can make a good zombie or other post apocalypse game a great one, and keep the group coming back (from the dead?) for more.
A young girl with a dirty face and tattered dress stands near the town market offering to sell the PCs freshly cut flowers. They are only a single copper a piece, and smell nice. Perhaps the PCs will be generous with their wealth, or they will not. Great for paranoid parties.