First of all, ignore all the snide and unhelpful comments, especially from the pretentious buggers who insult RPers because they think there's something superior about arguing their whackass political views rather than creative writing.
Second of all, it's up to you. If you want to debate politics, General is the go-to place. International Incidents and NationStates are for you to RP (that is, roleplay) with your nation. Portal to the Multiverse is also an RP forum, but for RPs unrelated to your NationStates nation.
Before posting in any forum, it's a good idea to read the threads at the top of the forums, or stickies, which tell you about that particular forum's rules. As well as General and the RPing forums, there is Forum 7, which is for random shit that doesn't fit anywhere else, and there's Arts & Fiction, which more or less speaks for itself. Factbooks & National Information is for posting information about your country.
Global Economics & Trade is about business-based RPs regarding your country, where you 'buy' and 'sell' stuff. NS Sports is for RPing sporting events.
You can also join the WA, which is our version of the United Nations. This allows you to vote for resolutions and stuff, I'm not a member so I don't know much beyond that.
Finally, there's the Gameplay aspect of NationStates, which we don't talk about here on the forums because even the RPers, F7ers and Generalites tend to agree that the people who don't post on forums and do these funny things called raiding and defending are just plain odd. I gather it has something to do with the WA.
For further information visit the
FAQs page.
Finally, good luck and welcome to NationStates