There's an easy way to nip this problem in the bud; stop giving your players experience points.
|You can crunch the numbers of you want, but I'm telling you, this is WAY easier.|
XP Causes More Problems Than It Solves
What do experience points do? Well, ideally, their purpose is to represent how much stuff the PCs have accomplished, thereby showing they've come far enough in this campaign that they need access to more class levels in order to continue. It's a gauge that shows how powerful your PCs should be at this stage in the game.
However, because XP can be granted by doing almost anything, it's not long before it becomes a meta concern. Players know they can sneak past an encounter, or solve it diplomatically, but will they be docked XP if they don't kill the bad guys? Sure, they might know that this group of guards is way too low to be a threat to them, but hey, they're almost to the next level and it might be just enough to push them over that peak. What about that town of commoners? Sure they might not be worth much, but that troll-blooded dragon just kicked their asses, and they need all the help they can get.
|If we burn down the forest, we'll get XP for EVERYTHING in it!|
If you want players to take the decisions that make the most sense for their PCs, or which make the most strategic sense, or which aren't blatantly evil in the pursuit of XP grinding, the obvious answer is to just take away experience points. Once there's no more counter keeping track of who killed who, or who disarmed which trap, you've done away with what can be a problematic motivation.
What Do You Replace It With?
Here's a new term you're going to learn to love as a DM; Milestone Leveling.
Milestone leveling is just what it sounds like; once players reach a certain, pre-determined milestone, they level up. It doesn't matter if they slaughtered the entire cavern of orc warriors, made peace between them and the human town, or hired them all to be personal bodyguards; if the plot has been solved, and the story is progressing, boom, the party levels. Even the players who missed a session or two. Even the ones who maybe didn't do as much damage, or contribute as much. Everyone levels.
|I repeat, everyone.|
As the DM, you can set whatever milestone you want for the little leveling button. It could be every third session, like you see in Pathfinder Society. It could be whenever players complete a certain plot arc, or just whenever you feel like chucking bigger, badder beasties at them. It might even be as a reward for doing something clever, or unexpected.
The point is that if players know their actions will not lead to the direct reward of more experience points, then they're more likely to do what comes naturally, what suits the story, or what's smart, instead of what will ensure they get another level. Because when you reward a behavior, that behavior continues. Even past the point of logic, sense, or alignment shifts.
That's all for this week's Moon Pope Monday installment. I hope it was helpful for my fellow DMs out there, and that if you try it you find it helps your games. If you want to keep up-to-date on all my releases, then follow me on Facebook, Tumblr, and Twitter. And, if you want to do your part to make sure Improved Initiative can keep giving you great content like this, head over to The Literary Mercenary's Patreon page. All I ask is $1 a month, which helps me pay my bills, and which will get you some sweet gaming swag just for becoming a supporter.