The next 10 - 15 days (like the past 10 - 15 days) are a very busy time in New York City. December is by far one of the busiest months in New York City for restaurants and hotels. Things go off a cliff in the new year and then most of January and February are quiet before business begins picking back up in March.
Make reservations easily without having to make any international long distance phone calls. Simply visit opentable.com and register for free. You can check availability and make reservations at a significant number of New York City restaurants.
Look beyond the touristy areas for the best food and the best value. Places like Little Italy and Times Square are generally going to be the most expensive, lowest quality, and the least value.
Explore neighborhoods a bit off the beaten path where you'll find amazing restaurants with great food, excellent service, wonderful atmosphere, and tremendous value for your dollar.
One of my favorite new restaurants in New York City is Spina. The restaurant is located on Avenue B and East 12th Street in the East Village. It is easily accessible by walking about 12 minutes from Union Square or simply changing to the fast and frequent L train and getting off at 14th Street / 1st Avenue (then only a 5 minute walk). Spina makes their pasta in the restaurant. The wine list has some exceptional values. This is such a charming restaurant with such good service. I've been back three times now and I know it wasn't a one off.
Also, in the East Village along Third Avenue (sort of an unusual spot) is a restaurant called Apiary where the fish and the meats are simply perfection. It is a great spot because I don't think it is someplace most hotel concierges would think to recommend - it isn't that small but I just think it is most NYC people. I would think it would be a little busier at the usual tourist restaurants and maybe slightly easier to get a reservation at a place like Apiary during the holidays.
There is a restaurant called Cafeteria on 17th Street and 7th Avenue in Chelsea. Cafeteria is open 24 hours a day and their Mac n Cheese is to die for. They really specialize in American comfort food in an upscale setting. Breakfast at Cafeteria is really a must. There may be a bit of a wait on peak days and at peak times but it is oh so worth it. It is just a really fun place. No reservations. Credit cards are accepted.
I like Philip Marie on Hudson Street for Brunch and I also like the weekend Brunch at Flea Market (a restaurant - nothing to do with a flea market) on Avenue A in the East Village. They annoyed me by charging extra for honey but I cut them some slack. On the Upper West Side, a restaurant called Good Enough to Eat always has a line out front but it is oh so good. Clinton Street Baking Company on the Lower East Side is widely regarded as having some of the best pancakes around.
Back to lunch / dinner, sometimes you just want to save a few bucks but you don't want to eat a $1.00 slice of pizza. There are places like Bennie's Burritos, Harry's Burritos, and Blockhead Burritos (multiple locations). I don't think you can get better or less expensive food in Mexico - so good. No reservations. Credit cards are accepted.
Sometimes you're craving good Chinese or Thai food and there are so many good choices. One of my favorites is Charlie Mom (more than one location I think). The great thing about the one in Greenwich Village is that it is across from Sammy's Noodle Shop and they compete head to head - keeps prices low and service / standards up. Spice has about 5 or 6 locations and things like the Jade Seafood Dumplings appetizers for $5.00 and the Pad Thai is amazing.
Don't limit yourself to Manhattan. A restaurant recently opened in the hip Williamsburg neighborhood called Miranda. I was a bit skeptical about the blend of Italian and Dominican but it blew my mind. Great service, excellent wines, very reasonably priced in a great setting. Steps from the L train at Bedford Avenue. Charming neighborhood and absolutely no safety concerns venturing into Brooklyn (I know visitors always think, hmm, leave Manhattan at night??? Busy part of town and very safe at all hours - just saying in case the thought crossed your mind).
Fifth Avenue in Brooklyn has lots of good restaurants.
Say you really want to venture off the beaten path - there is this awesome restaurant called Northeast Kingdom off the L train at Jefferson Street. It is 18 Wyckoff Avenue. Your first reaction when you step off the subway may be, OMG! Where are we? Well, you're definitely not in Kansas anymore but the restaurant is right there and the neighborhood is really coming to life. It used to be no-man's land. I suppose it was always safe only because of its desolation - the only danger may have been getting lost there and not being found for days. But now it is where all the young artists and musicians are moving.
There are also a number of cool wine bars in Manhattan. 8th Street Wine Cellar is one of my favorites. Terroir in the East Village is great (if you can get in). Best to try Terroir before dinner as it is always packed later. Xai Xai specializes in South African wines in Hell's Kitchen. I recently learned about corkbuzz on East 13th Street and plan to check it out in the new year.
You can always check these places out on menupages.com and visit their websites.
I hope this small sample of some of my favorite places has been helpful.