So, you want to see the Museum of Natural History, never been before.
It’s too big to see in one visit, so set some limits: you’ve got to see the dinosaurs (top floor), you might as well check out the stuffed mammals (main floor) if only because the artistry of it is so high-end—fabulous dioramas. There is even a family of dusty, dead elephants. Sadly, the gem gallery is now closed indefinitely for renovation. At that point I would be done, fini. For the day.
(By the way, be sure to find the titanosaur who is so big she occupies two rooms. So big you might walk under her and not notice. Biggest reptile ever.)
There is a restaurant in the building, but I suggest you move on, across the street, to the New York Historical Society. Much lighter weight than AMNH, but in it is a really nice restaurant. So go there, eat, gnosh, whatever, then see that museum too.
NYHS puts on pocket sized exhibits of importance—Vietnam War, New York’s role in WW2, and exhibits based on other culturally and socially relevant topics. Fewer visitors, no lines… it’s calming, in fact.
You can pay by donation at the AMNH, pay the cover charge at the NYHS, have a meal in a luminous, high ceilinged room and move on, refreshed, relaxed and much the wiser. Two museums in what, a day? Half a day? That’s efficient and fun.
Central Park is right across the street.