Don't Panic! Yes, others have said it, but I'm saying it again because it is important. Personally I love it when the group does something I haven't considered.
- Don't set up conclusions based on what the PCs will do. Give them a conflict or problem and see what they would do to get by it. Lets say the lord of the keep says they've been having trouble with an orc tribe. They've taken over an old keep and keep raiding out of it. Rather than try to figure out what the PCs are going to do, just detail the keep loosely. The players might try a frontal assault, or a trojan horse, or simple diplomacy, or a night-time raid, or something that you've never considered. You're just introducing a problem without a pre-concienved solution. Let them go at it!
- Your notes don't matter. Unless the PCs have interacted with it in some way, what you've prepared is irrelevant. If they run into a band of orcs and comment "That Duke Dastardly must have hired the local tribes to make the roads more dangerous, so the King will give him more troops!" That's much cooler than what you had planned, so thinking quickly you say that there's a bag of coins from the Duke's mint on the leader. The players think its cool and they think they're clever for figuring out your Evil Master Plan.
- About Evil Master Plans, even if you don't have one always act like you do. When the chance comes you can tie everything together to make it look like a carefully crafted plot, while the players have had complete autonomy the entire time. Love it!
- When in doubt, ninjas attack. Or orcs, or zombies, or whatever as your game dictates. You can figure out why they're attacking later, if anyone cares.
- Don't be afraid to ask for a few minutes to think about things. The players won't feel bad for you, they'll feel good about themselves for stumping the GM!
- Don't set up conclusions based on what the PCs will do. Give them a conflict or problem and see what they would do to get by it. Lets say the lord of the keep says they've been having trouble with an orc tribe. They've taken over an old keep and keep raiding out of it. Rather than try to figure out what the PCs are going to do, just detail the keep loosely. The players might try a frontal assault, or a trojan horse, or simple diplomacy, or a night-time raid, or something that you've never considered. You're just introducing a problem without a pre-concienved solution. Let them go at it!
- Your notes don't matter. Unless the PCs have interacted with it in some way, what you've prepared is irrelevant. If they run into a band of orcs and comment "That Duke Dastardly must have hired the local tribes to make the roads more dangerous, so the King will give him more troops!" That's much cooler than what you had planned, so thinking quickly you say that there's a bag of coins from the Duke's mint on the leader. The players think its cool and they think they're clever for figuring out your Evil Master Plan.
- About Evil Master Plans, even if you don't have one always act like you do. When the chance comes you can tie everything together to make it look like a carefully crafted plot, while the players have had complete autonomy the entire time. Love it!
- When in doubt, ninjas attack. Or orcs, or zombies, or whatever as your game dictates. You can figure out why they're attacking later, if anyone cares.
- Don't be afraid to ask for a few minutes to think about things. The players won't feel bad for you, they'll feel good about themselves for stumping the GM!