There are a lot of techniques, but in the end it all boils down to reading the other person's mind.
For example, then used Intelligence, you might get an information about spies enemy player operate, especially about layout of spies.
But it's not always clear why enemy specified that layout.
In the first place, there is no guarantee that a friendly Spy can always obtain an enemy Spy's layout by fraud.
Also, even if all the information is obtained, even if the enemy tries to show all the hands, the information will be different from the plan that the enemy was trying to realize.
The spy extracts one aspect of the situation where the plan is progressing to some extent as planned, but part of it is broken due to lack of control.
So the ability to analyze information obtained by spies will be very important.
And the ability to derive reasonable solutions from the analysis results, realize and implement them is also important, although it has a lower priority than the analysis of information.
For example, an enemy may destroy your goods because they don't want you to invest in something else.
If this guess is wrong, even if the subsequent action is not useless, only a low effect can be obtained, so the priority is inferior ( In actual play, please think more abstractly, such as "some purpose for destroying my goods", and please expose many potentialities ).
Even at this point, there are several strategies that can be considered in the abstract.
For example, if the main goal of the enemy is the destruction of your own country, you will need to resist thoroughly, but if enemy plan to continue using you from the beginning until the end of the game, there is a high possibility that you should be able to build a mutually beneficial relationship without control.
And, if there are explicit or implicit conditions for enemy, then you satisfy the requirements, they might still be able to build a mutually beneficial relationship.
