Government is a set of rules agreed upon, and politics is how a society determines those rules. So how do you create the systems by which civilizations negotiate those levers of power in your fantasy or sci-fi world? On the sliding scale of representation to authoritarianism, where do the civilizations in your world fall -- and why? What pressures have shaped society to behave in the ways that it does? How centralized or de-centralized is it?
So much of this can depend on the matrix of identity: the question of who gets to participate in government. Sometimes that's the official government, and sometimes that's the back-channels and shadow governments. And -- how much sense does your government really have to make, considering the real-world examples we have to draw from? Dysfunction can be every bit as authentic as function -- and often a lot more interesting for your plot!