Have you ever wondered how can you protect yourself against a new player who may choose to break a deal with you in the current game? If you have never played with this player before, how can you discover what type of a player he is? What if you agree over something with him, and he comes back denying it later on? You could end up in trouble. Is there a technique that you can use to know if he has a tendency to stab you in the back? It turns out that there is indeed an effective method.
To know if a player is thinking on plotting against you, you can put him in the same situation, though without alarming him to what you are up to. You don't want him to feel that you are accusing him, though you want to put him in a particular state of mind so that you can examine his reactions. This technique is called Similar Scenario.
Here is an example on how it is carried out. Suppose you are playing Risk with a new player. You may simply say "In my last game, there was this guy who broke his deal with another player. Wow, it was amazing to watch this back-stabber. He eliminated a couple of players by breaking their deals. He went on to win the game. Smooth...!". Now, watch his reaction. No one likes a back-stabber. You are just trying to sound positive on the subject and see how he will react. If he agrees with you and supports the idea, you will know that he might break deals when he gets an opportunity.
On the other hand, if he starts to disagree with you, he is probably not that type of a player. The difference between the two reactions is large enough so that you can easily spot the type of player.
As another example, suppose you want to know if someone is planning to follow the 'turtle strategy'. The turtle strategy is a strategy of isolation. A player simply accumulates armies in isolation and doesn't care about conquering continents. His defensive move is to make a suicide on anyone who attacks him (See Total Diplomacy, section 4.7 for more details).
This type of a player is usually annoying for others as they can't afford to remove him as there is nothing to gain. On the other hand, he become a bigger threat every turn. Suppose you want to discover if a player is planning to play the turtle strategy. What would you say?
You can use the Similar Scenario Technique describes above. You want to put him in the same situation and see how he reacts. You can say, "A friend of mine was playing Risk a few weeks ago and he told me an interesting story. He said that they had a player in the game that didn't attack anyone and simply kept growing every turn. He slowly became more powerful until he was a threat to everyone, but no one dared to attack him. My friend said, everyone was wondering how to handle him since no one wanted to spend their armies. Eventually, the annoying player won. Ever since he told me this, I have been thinking about it. What do you think they should have done?"
Now, if he was planning to follow this strategy, he may feel a bit uncomfortable as to what to say. He can't give you a counter-strategy if he is going to use this himself. He will be practically telling you what to do to stop him. In contrast, if he is not going to adopt the turtle strategy, he may suggest valid solutions to deal with such players. By analyzing his reaction, you can tell the difference between the two types of players and make your moves accordingly.