I have never been so any wise words of wisdom?
If you join one of the free tours of the Metropolitan Museum of Art, be prepared to walk very very fast, the place is huge and the tour guide covers a lot of ground quickly.
If you are going to ride the subway I'd recommend watching some YouTubes about it and also the subway's website's video. My first trip to NYC I got confused by all of it -- took the wrong train, took the right train in the wrong direction, didn't understand the difference between local and express trains, thought I was on the subway train but turned out to be on a real train and I didn't have a ticket and had to desperately look for cash, etc. But when I went back again I got so good at riding the subway (i.e., had figured out the Google maps app was telling me exactly the sign wordage to look for) I helped another person find the right train!
If you have enough time before you go, you can apply for the senior fare, and then you can electronically attach that to your method of payment to get the senior rate when you tap to get into the subway station.
The "Tenement Museum" has some interesting tours.
The NY Public Library docent led tour was really interesting.
I took a walking tour on the High Line which was okay but only did a portion of the park trail.
The Morgan Library and Museum tour was nice.
The lighthouse museum on Staten Island was not really worth the effort, but I wanted the experience of riding the Staten Island Ferry so I was glad I went.
Walking across (or partly across like I did) the Brooklyn Bridge made a good memory.
I enjoyed taking the tram to Roosevelt Island to look at the small pox ruins, though I wouldn't recommend it unless you like contemplative experiences (mostly I wanted to ride the tram, but contemplating the ruins has stuck in my memory).
In some areas of NYC, it was faster to walk places than to take the buses (due to the traffic congestion).
I'd heard good things about the Brooklyn Botanical Gardens, but I accidentally went to the NY Bronx Botanical Gardens instead, which involved way too much walking (the place is huge) but I was there in the spring when the lilacs were blooming and there was a whole area full of various kinds of lilacs and that was awesome.
I very highly recommend trying the "hand rolled" "kettle boiled" bagels that you can find in NYC.