Anywhere civilization starts to crop up people tend to group together. The exact definitions of a group of people can be a little vague. You might have people who are grouped together in a town, or in an occupational group. And how a group is managed and how they make decisions together is where politics comes into play.
Politics sound somewhat complicated, but they don’t have to be. In essence politics is how a group makes decisions. This ties partially into how they’ve organized any governing system. Are they held by a single leader, or do they follow more democratic or oligarchical structures? It also ties into cultural beliefs. Places where politics and religion aren’t separated may have some of those choices heavily influenced by a religious group or influence. And where there is a separation, any clash between differing beliefs can cause smaller political problems, even within the same group.
To start figuring out politics, it may help to start with the large picture such as your kingdom or country. The group decisions there are often about how to keep the kingdom and country running. This covers everything from who can become a part of the governing body, to how laws are agreed upon and who can trade with who.
From there take another look at how your group can be divided up. Consider things like religion, social and economic standing, educational level, age, gender and race. Smaller groups within a larger may have different views, and some of the political issues that crop up are the result of conflicting views. How do these smaller groups make themselves heard to the larger group they’re contained within? How do they influence the choices made by their governing body?
Once you have an understanding of how the large group works, consider how it interacts with other groups of the same size. This is where your different countries and varying types of government come into play. Even between groups with the same type of government system, their politics may change; one place may allow certain things where the other bars them.