The Breznial Kingdom: A case study in how not to run a kingdom from the perspective of a corrupt castle-wide conspiracy to strip their queen of any power.

1. Regardless of your eventual intent, your monarch is the face of your kingdom. Though it may be tempting, it is a bad idea to imprison her to be used solely as a puppet ruler. Maintenance is high.
2. Similarly, while it may seem a logical way to maintain power over your population, in the long term it is not advisable to keep the citizens in your castle cloistered away from the outside world. Doing so requires maintaining a very content population with very low education as a means of stopping them from asking inconvenient questions.
3. Know your people! If, for instance, it turns out the citizens behind your castle walls love their queen more than they love you, it may become increasingly difficult to ensure she remains the face presented to the people when your decrees are made through her.
4. While a well-prepared and equally corrupt military force is required to keep your puppet queen in check and dissuade your castle population from getting too intelligent and asking too many questions, it is a good idea to deploy some of them to maintain some control outside the castle as well. Failure to do so (in effect, abandoning the outside population) may result in a lawless, chaotic landscape run by gang lords and violent crime, which may eventually prove economically detrimental.
5. Know the people outside your castle! If you fail to maintain order, it is acceptable, though perhaps not preferable, to contract the services of said gang lords to do any questionable work needed to be performed outside the castle, or even in other nations. However, you should know their limits; a well-armed neighboring military force may not take it well if gangs of low-level thugs start causing trouble at the borders.
6. Building your castle on the edge of swampland is tactically beneficial, presuming you can do so without the castle burning down, falling over, and sinking into said swamp. After all, taking advantage of difficult terrain is one of the keys to any military victory. Just make sure your own troops can navigate the swamp with ease, else you may find yourself cornered in the event of a successful siege.

We hope these lessons set you on a good course to your own corrupt government takeover!