If you are heading into NYC by rail, in particular Amtrak from points north like Albany (and that corridor is getting very popular so I bet your out there) did you know you can get to Grand Central Terminal (GCT)? Yes, Amtrak only serves Penn Station in NYC, but Metro-North goes in to GCT. Sometimes it easier to go into GCT then Penn, like if one wants to stay at the Marriott on Lexington Ave. Amtrak and Metro-North both fail to mention that Yonkers and Croton are the only two stations they have in common
If you want to get into GCT from Amtrak inbound from upstate, just get off at the Croton-on-Hudson station and grab a south bound Metro-North (MTA) train of which there are lots of during business hours.
Metro-North is commuter rail so travel with a carry-on and a laptop bag is reasonably comfortable and you’ll get into GCT instead of Penn.