As a frequent (but never frequent enough) visitor to NYC, I'm constantly looking for a place to leave my backpack for a few hours. I know that I'm not alone, and people who aren't enlightened that travel with suitcases
sometimes need to ditch those, too.
My friend lives in The Bronx, and has passed on this piece of advice to many, many visitors and residents alike. I used it last time I visited; I had a night flight out of JFK, but didn't want to return to The Bronx from Manhattan just to collect my things:
At Penn Station, near Amtrak track #5 , there is a "parcel check" service at which one can check baggage to be held for pickup later. The cost is around $5 per package. Recently, I have not encountered any requirement to purchase or show an Amtrak ticket in conjunction with this service. Even if there were, I suppose one could purchase a cheap Amtrak ticket and still spend no more than $10 or $15 to store a bag.
Since lockers are scarce-to-non-existent in New York, what other tips can you provide on storing luggage in Manhattan and elsewhere in NYC?