Guest Author - Jay Shaffstall
We've all had the experience where we're watching a move, or reading a book, and before you're a third of the way through you have this insight. You know exactly what sort of plot twist is going to happen toward the end of the story.
Your players are the same way.
Whenever you come up with a plot twist for a role playing scenario that you think, "This is really cool!", the chances are good that your players will see it coming a mile away. The problem is that the really cool plot twists are cool because they tie into other plot elements well, and that makes it easy for someone who is well versed in plot twists to see them. And anyone who has grown up in front of a TV or with a book in their hands these days is well versed in plot twists.
To truly surprise your players, you must do the unexpected.
I find that the easiest way to surprise my players is to not plan my plot twists out in advance. After all, if I'm planning the plot in such detail that I already know what sort of twist will happen near the end of the story, then I'm probably not taking into account what the player characters will do. And reacting to what the PCs do can result in the most satisfying twists of all.
For example, let's say that you know that the villain is the mayor who hired the PCs to save the village from the goblins. The mayor had a deal going with the goblins to get revenge on the other villagers, who were planning on sending the mayor packing. The players will learn all this, and suspicion will fall on the mayor.
Nothing wrong with that. That isn't the twist, that's just part of the story. The twist comes when the mayor's daughter falls in love with one of the PCs (who had been flirting with her throughout the game). The mayor's daughter discovers her father's plot and travels to warn the PCs, getting captured by the goblins as a result.
By taking into account what the PCs are doing, and then having NPCs react in believable ways, you can often throw plot twists at your players that they won't expect.
The key to this is role playing the NPCs. A plot twist that you develop from start to finish as you're planning the story is the product of your mind trying to fit all the pieces together in a neat and orderly way. A plot twist that arises from the motivations of the NPCs is not going to be neat and orderly. It'll complicate the plot needlessly when an NPC does something because that's what she would do.
The players can't look inside the NPCs' minds and personalities the way you can as GM. They don't know that the mayor's daughter is a bit obsessive and tends to overdo everything. You do. Or at least you do when you decide that's the case halfway through the game, when it'll complicate the PCs' lives to have her show up as they're battling goblins.
So don't try to plan out every twist and turn of the plot ahead of time. Give your NPCs enough rope to trip up the PCs, and then pretend that's what you had in mind all along.