You’ve made your world and have been running your game. You come to the point where the players are now off your initial map. This is a make or break moment for your game. What you add to the game at this point can change the pace and atmosphere of your campaign from this point on. Adding the wrong ruins or an out of place city can completely undermine the narrative of the story you’re trying to tell.
At this point, as you’re expanding your campaign map, you have to ask yourself ‘how is this going to affect the story I’m telling?’
Say you’re adding a ruin that was previously unknown to your world. Why is this ruin there? Why does no one know it exists? And, most importantly, why are your players going?
Look at it this way: You’re running a horror campaign. The players have spent most of their time in graveyards and haunted castles. They’ve explored everything you had planned initially and you need to add more for them to keep playing. You could have your players explore a volcano inhabited by titans and elementals or you could have them explore the tomb of a lich. One of these two is more in line with the themes your players are used to seeing.
To make things a bit more specific, you’re running a post-apocalyptic WoD game. You’re players have been struggling to survive. They have travelled across the irradiated wasteland; carefully managing they’re food, water, and resources. One day they find a shelter with enough food and weapons to last them for years. Unless you have a plan for this, it undermines your entire campaign. It could become an interesting turn in the story, if you work it right. Maybe people attack them to take their new goods. Maybe the owners of the shelter come back. Any number of things can happen, but the point is, you shouldn’t add this sort of thing to your campaign without knowing how you want it to play out.
Always remember, no matter where your game goes or what happens, the story is the most important part. If your story suffers, your whole campaign will suffer. Don’t let your narrative suffer, always ask yourself not just how a new addition to your world can affect your story, but how can a new addition improve your narrative.