It depends on where in Queens you're coming from. But not too many subway lines run through Queens, so there aren't that many options. See the Related Link below for a complete New York City subway map.
Option 1: The F or M trainsTake the Downtown (Manhattan-bound) F or Mtrains (of the B-D-F-M, the orange line) to 34th Street-Herald Square (at Broadway).
Option 2: The E trainTake the Downtown (Manhattan-bound) E train (of the A-C-E, the blue line) to 34th Street-Penn Station (at 8th Avenue).
Option 3: The R trainTake the Downtown (Manhattan-bound) R train (of the N-R-Q-W, the yellow line) to 34th Street-Herald Square (at Broadway).
Option 4: The 7 trainYou can take the 7 train (the purple line) to 74th Street-Broadway. You can transfer from the 74th Street-Broadway Station on the 7 train to the Jackson Heights-Roosevelt Avenue Station on the E, F, M and Rtrains. Then you can take the E to 34th Street-Penn Station (at 8th Avenue), or the F, M or R trains to 34th Street-Herald Square (at Broadway).
Or, you can take the 7 train to 42nd Street-Grand Central Station, and transfer there to the Downtown 6 train, one stop to 33rd Street (at Park Avenue South).
Or, take the 7 to 42nd Street-5th Avenue. This station is connected to the 42nd Street-Bryant Park Station on the B-D-F-M (the orange line). Take the Downtown B-D-F-Mone stop to 34th Street-Herald Square (at Broadway).
Or, take the 7 to 42nd Street-Times Square, and transfer there to the Downtown 1-2-3 one stop to 34th Street-Penn Station (at 7th Avenue).
Take the S shuttle train (color grey), or the 7train (the purple line) if the shuttle isn't running, from 42nd Street-Grand Central to 42nd Street-Times Square.
Transfer at 42nd Street-Times Square to the Downtown 1-2-3 (the red line), 1 stop, to 34th Street-Penn Station (at West 34th Street and 7th Avenue).
Take the Downtown 6 local train (of the 4-5-6, the dark green line), 3 stops, from 42nd Street-Grand Central to 23rd Street (at Park Avenue South).
You'll exit on the west side of Park Avenue South. Walk 2 1/4 avenue blocks west (3 1/4 blocks if you count Broadway, which cuts between avenue blocks) on 23rd Street to 16 West 23rd, between 5th and 6th Avenues.
Yes- Grand Central Station is the name of the SUBWAY station which is below ground (4, 5, 6, 7 and "s" 42nd St Shuttle lines). The RAILROAD station (MetroNorth Railroad) is known as Grand Central Terminal and is at street level.
VIA subway
Not possible these days. Amtrak no longer has service to Grand Central Terminal. BTW - Grand Central Station is the subway station. The railroad station is Grand Central Terminal.
Grand Central Station
Grand Central Station & Terminal are located at East 42nd Street between Park and Lexington Avenues. Grand Central Station is the subway station, where you can catch the 4-5-6 (the dark green line, aka the Lexington Avenue Line) or the S shuttle train to Times Square. Grand Central Terminal is the railroad terminal, for trains that are not part of the New York City subway system (like MetroNorth commuter trains).
Grand Central Terminal is the name of the railroad station at 42nd St/Park Avenue. Grand Central Station is the name of the subway station which is below Grand Central Terminal.
Take the Downtown 4 or 5 express trains (of the 4-5-6, the dark green line), 3 stops, from 42nd Street-Grand Central Station to Fulton Street (at Broadway).
No, they are two separate subway stations.
No, but it does stop at penn station and you can take the subway
There is no train that runs directly between Penn Station and Grand Central. You have to take the subway: the Uptown 1-2-3(the red line), 1 stop, from 34th Street-Penn Station to 42nd Street-Times Square, then transfer to the S shuttle train (color grey) to 42nd Street-Grand Central.Trains on the New York City subway system operate continuously. There are schedules you can download, but they're often inaccurate.
take the Shuttle or 7 train from Grand Central to Times Square and transfer to the 1 train uptown to 59th Street/Columbus Circle
According to Wikipedia and the MTA themselves, 77 of New York City's subway stations have working bathrooms, and 28 of these stations are in Manhattan. However, according to the Related Link (see below), in Manhattan, only 8 of these stations are actually functioning and open to the public (9 including "the developer-financed wonder bathroom at the Times Square Station"). The only one on the 6 line is the Brooklyn Bridge-City Hall Station. There are also bathrooms at Grand Central Terminal, downstairs, near the food court. The 4-5-6 line stops at 42nd Street-Grand Central Station, but Grand Central Station is the subway station, while Grand Central Terminal is the railroad station. So, you would have to exit the subway system to use the bathroom, and then pay another fare to get back on the subway.