How actions work:
Actions should explain how the goal is achieved. For example, writing "I invent gunpowder" won't do much. If you do something like "Seizing enemy cannons, we figure out how they work so we can use this technology," or another way depending on the context, the action will have a better chance of succeeding. Some actions might not succeed; if there is a level of uncertainty, I will roll to determine its success.
To conduct diplomacy with other nations, post in the thread. Diplomatic actions will not count towards the limit per turn; they are free.
When diplomacy fails, war begins. Most wars will only last one turn, so you're entire strategy should be included with the declaration. Make sure you also include what you want out of the war as well. While your nation is in a state of war, your issues will display your level of war exhaustion. If a war drags on for more turns, or you start another war a turn after the previous one ended, the war exhaustion will increase. War exhaustion will cause your nation to perform worse. Side effects may include economic turmoil, depopulation, and revolts (see "revolutions" for more information). War exhaustion affects nations differently depending on size, as a smaller nation likely does not have as many resources or manpower than a larger nation, which could handle high war exhaustion and even defeat without collapsing.
The differences of how actions work from nation to nation:
Unitary states are nations which only have a single government; although autonomy can be given to certain regions, they are not controlled by the player. Actions for centralized states are more flexible than normal, and can apply to the local and the national level.
Federations have a national government and states with their own governments. Actions on the federal level apply to the entire nation (war, diplomacy, international trade, etc), while states focus on more local issues (infrastructure, water supply, trade between states, etc).
Confederations are somewhere between an alliance and a federation. While an alliance is composed of independent states, and a federation can have a strong central government, a confederation has a government so weak that, when you send actions relating to the confederation as a whole, I'll count them as diplomatic actions, even if you send them privately. However, the member states' actions should be relevant to the goals of the meeting, in addition to local concerns. For example, if the confederation declared war, the state bordering the enemy can directly attack while other states can send manpower and supplies.
How different government types work:
Democracies include direct, representative, or other edge cases (see: oligarchies). These governments will tend to form political parties around certain issues. Public opinion is an important factor in determining the success of actions. If the public is positive towards your nation, then not only will actions have better chances of succeeding, but your people may contribute bonus actions which are not restricted by the usual limits. If public reception is negative, actions will have worse odds, and I will start rolling for revolts.
Oligarchies are characterized by power structures inaccessible to the majority of citizens, whether that be wealth, intelligence, age, military, or some other barrier. Like democracies, oligarchies can exhibit partisan behavior, but public opinion, while present, is usually irrelevant.
Autocracies are systems where the government has enough power to do whatever it wants within their borders, or one's borders, because they typically have a sole leader. This form of government is most unlikely to be partisan, and public opinion only matters under extreme circumstances.
Successful revolutions give your nation an opportunity to change its structure, and even culture, entirely. Democracies are most likely to have revolts, but they are far less risky than normal. As such, they are least likely to have a revolution, as citizens can typically find another way to protest. Autocracies can have revolts too, but it's unlikely for them to turn into revolution, as the government could simply suppress them before they go out of control. Oligarchies, while most likely to have a revolution, can put down revolts like autocracies, but may have to implement a few reforms here and there to maintain stability.
Anarchic nations can occur if a government collapses and nothing replaces it. Actions sent to the anarchy are treated more like suggestions, as the people will only respond to suggestions if it happens to align with what they want. Anarchy doesn't last very long, as an outside power could easily fill the power vacuum or the people begin forming more complex forms of organization that can no longer be considered anarchy, making your nation playable again.