Heading for New York, what to do?

[Fritz]

Bring weapons!!!
Just kidding.
Only if you ride our immaculate subways.

If you like opera or bway, you can usually find discounted tix.
The Gugg.
Folk Art Museum.
9th & 10th Ave for food if you want to avoid mid town insanity prices and crowds.
and below 14th.
There may some free stuff up at Lincoln Center in the eves.
And Battery Park City.  Central Park is cool, just watch out for cyclists.
In midtown especially be very aware of ebikes.
Prospect Park in Bklyn is rather lovely. Carroll Gardens and Park Slope west of the Park.  
As is Williamsburg. And Greenpoint north of Wburg.
Smorgasburg depending on the temp, in Marsha Johnson Park on the east river in the BK.
Good town for jazz.
Chelsea Market, though tending to be crowdy, is a fun hour or two with lots of food, fashion & smurfs.
LI beaches are nice depending on where you are.
Unless you have a "mission" I'd avoid the Apple stores.
Try to avoid Times Square area.  There really is nothing to see there but crowds, foreign tourists, scams and shams.
Unless you go at 3am, when it's still crowded, but even more uninviting.
Don't go see a TV show being shot of any kind.  Trust me or bring a can of paint.