As I write my story I ask myself ten questions about the world I'm creating. There are several hundred questions you can ask when creating a world, but if you start with these ten you can get a good basis for what you want the world to be.
Each question is a generality, and there are many more questions that can be asked, these are only the starting points of world building.
1) Is there magic? (For my stories the answer is yes nine times out of ten. If yes, how is it controlled, who controls it, what are its limits?)
2) What kind of government is in control? (Monarchy, Democracy, Anarchy, etc. This question is where a general knowledge of government does help. This can be obtained in a high school government class or just googling online.)
3) What is the physical environment of the story like? (Forest, Mountains, Desert?)
4) Directions? Which way are my characters traveling to get to where they're going? (This is where it's helpful to draw a map)
5) Buildings and building materials? (Are the buildings made mostly of stone, wood, reeds? Are they grand museums or little huts?)
6) Is there technology? (In my stories, nothing beyond what was around in medieval times most of the time.)
7) What kinds of creatures occur in this world? (Are they the same as our world's cornucopia of animals or are they different? If they're different, how are they different?)
8) How many types of people? (Are there only humans, or are there (in my case) orcs, elves, fairies, etc.?)
9) If there is more than one type of people, how do they interact? (Not at all, at war, at peace?)
10) How is the land divided? (Is there more than one country in the story? Are the countries at war? At peace?)
Each question will be discussed in more detail.