I'm curious how you cope with misadventure in your campaigns. So you get a clearer picture of what I have in mind, here are a few examples:
1) Your adventuring party is traveling through a region where there was barely rain for the last few months. You decide to make a camp, light a camp fire, etc. Do you automatically assume the party took all precautions to prevent a fire? Say your party leaves the camp the next day, but didn't make sure the fire is completely extinguished. The party might leave the region in time and not notice what's happening or they might not realize they were the cause for the disaster.
2) The party is in a city/village and there happens to be a fight your party is involved. The wizard casts a firewall within the settlement. Adjacent buildings catch fire. In a worst case scenario a big part of the settlement might get ravaged by the fire.
3) The party is traveling on a road and get's waylaid by bounty hunters. During the fight the wizard casts a cloud kill which hits crops (or even cattle) that are besides the road as well as some attackers.
These examples may be a little too constructed. D&D rules, especially spells and their descriptions rather put a focus on internal game mechanics (saving throws / damage range / etc.). How do you cope with such situations? Especially how do you confront the party with the results of their actions?