House rules are like explosives. They can be a wonderful tool for GMs who need to tweak a system to better suit their game, but if they are used recklessly or are allowed to get out of hand then they can blow everything to hell. Here are some simple guidelines on how to safely and effectively implement House Rules in your game.
Guideline the First: Don’t house rule a new system.
This is probably the most important guideline for house rules. If it’s your first time GMing in a new system, even if it’s one you’ve played before, you probably don’t understand the rules as well as you think you do. It is very important to be familiar with a system and how it works if you’re going to start changing things. That’s why I consider it extremely important to run things pretty much by the book for the first few times in a system. RPG systems are kind of like habitats in nature. A house rule, even a small one, is like messing with an ecosystem and you need to understand that system before trying to change it.
Guideline the Second: Make sure you know what the rule you’re changing does.
This is another mistake that’s really easy to make. When I was new to gaming and GMing I would often look at a rule and skim over it and be like “I don’t like it, let’s house rule it to be like this.” I had no real idea if the rules were balanced or how well they worked. I didn’t take into account the fact that the rule was published in a system that had probably been extensively play tested. All I knew was that it sounded stupid to me so surely I could just change it and things would only be better for it. I was wrong, because I didn’t even understand how the rule worked. Speaking of understanding…
Guideline the Third: Make sure you understand why the rule you’re changing is (or isn’t) there.
One thing that’s easy to forget is that most RPGs have been written and play tested by professionals. This means that if a rule is in place in a system it’s most likely there for a good reason. It also means that if there is something that the rules do not allow for, it was probably left out for a reason. So when you choose to change something, make sure you understand why it is the way it is.
Guideline the Fourth: Make sure it is a functional rule if used universally.
If you make a house rule, make sure it’s something you want to be a rule in your game. Making individual exceptions for specific instances is different from house rules and should really only ever be done on the spot. For example “We’ll ignore that rule during this fight because none of us knew about it” is ok, but “We’ll change the way this class works but only for your character” is usually a bad idea. This goes double if you create a new class or special ability that only applies to an enemy NPC because it can throw the balance of the game off. If you make a house rule, you should make sure it’s something that you’d be ok with seeing used by any player. You don’t want a house rule that can be exploited, even if you don’t think the player who wants to implement the house rule intends to exploit it.
Guideline the Last: Talk to your players.
You really shouldn’t implement a house rule that your players aren’t comfortable with. You especially shouldn’t implement a house rule that your players are wholly opposed to. Finally, never EVER implement a house rule that your players aren’t aware of. This is important because when your players make a character for your game they need to be able to make that character with an understanding of how the rules are going to work. Otherwise you run the risk of your players being confused, or regretting a decision that they made during character creation because they didn’t know about a house rule that you threw in. This also means that if you have an established set of house rules you should make sure new players know about them and how they work. As a GM, it is your responsibility to inform the players about house rules rather than their responsibility to ask questions.
These guidelines should help you plan the house rules you put into your game and implement them responsibly. Every guideline I put here has come from a history of my own mistakes with house ruling. They may not be perfect, but they have worked very well for me and hopefully they will work well for others.