It seems everywhere you go that someone is telling you to say “Yes” to your players. Saying “Yes” is more or less de rigueur these days, and you can’t use an area of effect ability without hitting three members of Baker’s cult of “Say ‘Yes’ or roll the dice.”  Said too many times though, the simple “Yes” can turn even an excellent GM into a drooling bitter burnout, and it goes further than that. “Yes” waters down your game, stretches verisimilitude (haven’t heard that one in a while, eh?) and is a pitfall waiting to happen. There’s a place for “Yes” in every game, but given the current “say ‘yes’” culture, it’s easy to forget that there’s an equally important place for “No”.
When do you need to say “Yes” and when do you need to say “No”? Each has a place in your campaign and at your table and using the right one at the right time will make your job that much easier and your game that much better. It’s a good rule of thumb that the right time to say “Yes” is whenever it’s not the right time to say “No” but there are specific instances where each is particularly useful.
It’s the right time for “No” when:
- A player asks for is more work than you can currently handle – Biting off more than you can chew, even at a player’s request is a good way to become bitter, overworked, and burned out. Being realistic about your limitations and workload can keep your games and friendships running smoothly. Not doing so is a good way to bring your hobby crashing down on your head like a house of cards.
- The request requires more work than the potential payoff – If your player asks you for an entire rewrite of a base system when an existing option would be close enough, or wants you to insert their custom backstory or setting which would be an awkward fit at best it’s a good time to say “No” In some cases, the right answer is “Next time” but that’s just a “No” in disguise.
- It would ruin the mood and concept of your game – Of course, this assumes that you and your players are enjoying the current mood and concept of your game. If it’s time for a change, or you trust the player in question can handle the difficult element gracefully, like a well-timed comic relief character in a serious campaign, then by all means say “Yes”, but otherwise your answer should be “No” (or again, “Next time”).
- It violates your setting – Save this “No” for gross violations, but if something a player is asking for literally sticks out like a sore thumb and requires a block and tackle to suspend disbelief, it’s OK to say “No” (or, surprise! “Next time.”)
- It’s disruptive – Nothing about the “say ‘Yes’” culture makes or should make you a doormat. If a player is asking for something disruptive or obviously is just pushing something to be a jerk because they know you feel obligated to say “Yes”, it’s the perfect time for “No”, or ever “Shove it!” if you’re feeling bold.
- the fun is at the expense of other players’ fun – Unless there are extenuating circumstances, a GM has to balance everyone’s table experience, which means that you can’t allow a request by a single player to outweigh the enjoyment of everyone else at the table.
- You’d have to stray too far from your comfort zone – By all means, push your comfort zone , but don’t be afraid to say “No” when it’s pushed too far in a single go or when it’s too short notice.
It’s the right time for “Yes” when:
- It will make your game more fun – All other things aside, you’re playing an RPG because it’s fun, so if something a player wants will make the game more fun, go for it.
- A player has a good idea – Don’t begrudge your players their good ideas, not even if it prematurely offs a bad guy or circumvents an entire plot arc. You can always recycle the unused content .
- It’s influential and reasonable – Players only have so many ways to influence the game world. If what they’re asking for makes sense, why not give it to them, even if it’s not exactly what you planned for. Again, this may require some recycling, and some improv  too.
- When you’ve got nothing better planned – If you’ve got a blank spot in your game and your player asks if there’s a thieves’ guild there, put a thieves’ guild there. They probably asked for a reason.
- Because you asked for input  – Sometimes it’s fun to hand a bit of narrative over to a player: “Who owns the biggest ship in the harbor?” Unless the response you get is completely unacceptable “Space Elvis, who single handedly piloted his ship, the Millennium Falcon from Mars to pose as the second coming of Christ” then it’s sort of a dick move to say “No”. You asked for it after all.
- It’s not time to say “No” – As mentioned above, in general, if it’s not time to say “No”, it’s probably time to say “Yes.”
So saying “No” is as important as saying “Yes”, but they serve different functions. “No” is for preventing problems in your game, “Yes” is for embracing fun. Both are important tools and should be wielded carefully. But when uncertain, feel free to default to “Yes”. After all, you can always say “No” later.