The subway system in NY is one of the biggest in the world. Considering its complexity, it is pretty well organized, but be forewarned it can be a bit tricky if you are used to a simpler one (like i was in Barcelona). There are express trains that won't stop in certain stations, then some other trains are express only in certain hours, and then sometimes there are unexpected changes in the lines' routes, just to have some fun i guess :) To sum up, if you don't have your eyes opened all the time, it may get a little crazy! But most of all, the NY subway is an experience itself :)

Don't be left on the curb by taxi drivers who won't take you to your destination. By LAW they have to take you anywhere in the 5 boroughs. When you're asking for a far off destination (especially late at night) get IN the cab first and shut the door before telling them your destination. If the driver still gives you a hard time, ask for his License number. This threat should work.