The first thing I'm going to explain is how the subway system is set up. It's quite simple once you get the hang of it. Get out a map of NY or a subway map. You should notice central park smack dab in the middle. Central Park separates the east side from the west side i.e. east side is east of central park and vice versa. Mid town is below central park. There is some debate as to what street it begins on but a safe rule is that once you are in the forties, you're in midtown.
Most of you know that NY is setup in a grid, the streets start from 1st streets keep going till 200 and something or more in the Bronx. Downtown an be a little confusing as it has some streets that are not numbers. The avenues run from east to west. 1st avenue being on the east side and 9th avenue on the west. 5th avenue separates the east side from the west. Thus, it's hard to get lost in NY, you just have to be able to count.
Soho, Chinatown, Greenwich village and little Italy have a lot of restaurants and shops but can be trickier to navigate because the street numbers stop and it turns into names. You might need to refer to you map and ask people if you want to locate a restaurant or something in this area.
On to the actual subway. The key thing about using the NYC transit system is that you need to know where you are and where you are going. You need to know this because it determines whether you take an uptown train or a downtown train. For example if you are at grand central and you need to get to Harlem, you can take the 4,5 or 6. However, if you need to get to china town you can also take the 4,5 or 6. The difference is that Harlem (around 125th st) is ABOVE grand central (42nd st) and china town (under 14th st) is BELOW grand central. Thus you would take an uptown train to Harlem and a downtown train to china town. It's a good idea to note that it doesn't matter if you destination is located in a high or low street number, what matters is where it is located in relation to where you are.
You should know the difference between express and local trains. Express trains skip some stops. Sometimes A LOT of stops. Make sure your train actually stops where you want to get off. You don't want to attempt to go one stop and end up in Brooklyn. It's a waste of time. Some common examples: Although the 4,5 and 6 run a similar route, the 4 and 5 are express. Same thing for the 1,2,3 -the 2 and 3 are express.
That's it. You're ready to navigate the nyc transit system and enjoy your vacation. It's a fairly lengthy guide but hopefully it's helpful. Let me know in the comments if anything is not clear or you would like me to explain another point. I can always modify this.
