My wife and I returned from four days in NYC yesterday--our first visit.
Here are some thoughts--
1)negotiate everything even the bicycle guys
2) don't buy from the tour guys or sales people outside the various locations--go to the ticket window inside otherwise you will find you overpaid. Example the Empire State building.
3) Visit the Empire State building at night. The view is great then. Don't pay $15 extra to go to the 102 floor. The view at 86 does...