How does one begin to understand politics?

I am fifteen. I'm not completely ignorant, but I'm not as informed as I'd like to be, either. I'd like to be able to keep up with the economy, world affairs, important laws. And I'd also like to educate myself in political standpoints. I think I might be liberal, but I'm not completely sure because I'm not very familiar with other standings. Are there any, I don't know... books I can read? Articles? Movies? Where do I begin? Thanks in advance.