Let's say you had three full days in New York City. Here's what I would tell you to do.
Unpack and have something to eat near the hotel. Ask the concierge for the address of a local coffee shop (we don't have many diners in NYC; we're a coffeeshop culture). Pick up a copy of Time Out New York so you can see what the weekend looks like. A copy of the Times wouldn't hurt either. Read, and have a simple breakfast of regular coffee (milk, two sugars) and a toasted bagel with a schmear (cream cheese). spend the day wandering around the Upper east side. Look at the prices in stores and laugh. Get to the Metropolitan around 4:30 when most ofthe tourists are clearing out and go up to the balcony to have a drink and a snack at the bar that's set up every Friday and Saturday night. Feel very elegant and sophisticated. Wander through the Asian section and enjoy the Ming Scholar's Garden. Ooh and ah over the furniture rooms and wonder what it would have been like to be French nobility. See whatever big exhibit is on. Don't forget to pick up an audio guide on the way upstairs- it will be worth it. Leave as the museum closes, feel world-weary, and get in a cab. Go a nice restaurant - Artisanal is good. Have fondue. go back to the hotel and get some sleep.
Oversleep a bit. Get up and catch the subway. Go to Chinatown for a dim sum brunch. Buy some egg cakes from the street vendor, and maybe some snacks for later. Wander over to Di Palo's afterwards and buy Italian goodies for later. Wander around Nolita. Look at the original St. Patrick's Cathedral. Wander up into Soho. Go into Dean and DeLuca and laugh at how you spent less money on your sausage and cheese than the other tourists who bought things in there did. Grab a train and go uptown to Times Square and marvel at all the lights. Go listen to music in the lounge at BB King's. Go to your hotel, eat bread and cheese and sausage and biscotti from Di Palo's, and wash it all down with blood orange juice.
Find a coffeeshop and have a brunch with cheap sparkling wine. Go to the Upper West Side and visit the New-York Historical Society. Use this as an excuse to go to Knitty City and buy yarny goodness. Pick up some bagels to take with you. go back to the hotel and eat the rest of your bounty from Di Palo's. Be the happiest tourist in New York. On your way home, eat real bagels until they come out of your ears.