BARS & PLACES TO EAT ON 42ND STREET (212 EAST)
Your best bet is actually to *leave* the immediate area of 42nd St around 2nd & 3rd Aves. Most of the food in the neighborhood is geared towards the post-college crowd (Cactus Jack's) and the business lunchers.
You should definitely visit Grand Central Terminal, to see the renovated great room, the gorgeous marble, the antique chandeliers, etc. Some of the food in the lower level court is good, but mostly it's overpriced and not worth the trip. If you work here (like I do), it's handy; if you're visiting, keep on walking.
The exception to this rule is the Oyster Bar. If you enjoy raw oysters and/or raw clams, stop here for lunch. Sit *at* the bar (never at a table) & have a bowl of their excellent New England-style clam chowder and some raw stuff.
Otherwise, get a Metrocard & head for wherever the best of the best can be found. I see that you've got a UK email address, so I'm assuming you'd like to eat the things you really can't get in England?
Head to the eastern border of Chinatown & get dumplings at the Dumpling House (118 Eldridge St b/w Broome & Grand).
Stop at Katz's Deli for some NY-style sandwiches, especially the pastrami on rye. This place may look familiar to you - it was the location of Sally's fake orgasm scene in "When Harry Met Sally."
Wander around Greenwich Village & the West Village, licking a scoop of handmade gelato or sorbeto from Cones (272 Bleecker near Morton & 7th Ave).
Make your way to Ess-a-Bagel, at 359 First Ave @ 21st St, for a jumbo carb-laden NY bagel. I prefer to snack on these, right before I go to bed. Not good for my low-carb diet, but really good for putting me to sleep (via bagel-coma). If you can handle it, though, grab a bagel & cream cheese for breakfast & then walk it off.
You have to grab a slice of pizza somewhere - that's obligatory. The best slice is a matter for some debate, here on Chowhound. I'd recommend looking at some of Chicago Mike's "Pizza Safari" posts - he's done an almost-exhaustive (and exhausting!) review of loads of places all over the city. CTRL + F for "Chicago Mike" and you'll hit all of the good stuff.
Are there any other kinds of foods you'd like to try, while you're here? NY claims fame for its bagels, its deli sandwiches, its pizza . . . But what else interests you?
re: Victoria Quemby
These will just be *my* suggestions, mind you, but I would recommend:
A dim sum "brunch" at Ping's, down in Chinatown. 22 Mott Street between Mosco Street & Chatham Square. Right in the heart of C'town and an outstanding meal for very little money. Go on Sunday and plan to wait for about a half-hour, although if you get there at 11:30, you may get a table right away. Per person, expect to spend about $15 with tax & tip. Dim sum, by the way, is "small plates" of many different things - dumplings, buns, sauteed veggies, interesting & new Chinese specialties (such as chicken feet in sauce).
For lunch or dinner in Chinatown, I'd recommend Peking Duck House at 28 Mott (btwn Mosco & Pell). They're a little bit more like a "real" restaurant, rather than the down-at-the-heels joints often found in C'town. With alcohol, tax & tip, you'll spend about $30-40/person.
There have been dozens of posts on Chowhound about steakhouses & the outstanding winner always seems to be Keen's. It's been around since 1885 and you really can't go wrong, if you want "classic NY" *and* a great steak. 72 West 36th St btwn 5th & 6th Avenues. Call for reservations, without question. (212) 947-3636. Dinner will cost around $75-100/person with tax, tip, and 1-2 drinks per person. If you order bottles of wine, your bill will be more.
As mentioned before, you really should grab a lunch at the Oyster Bar in Grand Central Terminal. Spend some time in GCT, too, and really look at the wonderful architecture & artwork (I consider chandeliers to be "artwork"). If seafood isn't your thing, you could always grab a cup of matzo ball soup & a half sandwich on marble rye at Mendy's, on the lower level. Not the most elegant food to be found, but a wholesome meal & traditional Jewish NY. Average lunch per person = $10.
For a *better* traditional Jewish NY meal, head down to Houston & Ludlow, on the Lower East Side. Katz's Deli serves up old-fashioned NY attitude, along with the best hot pastrami sandwich in the universe and some terrific Kosher hot dogs (if you like that kind of thing). This neighborhood is home to loads of great bars & restaurants, as well as the Tenement Museum - an interesting view of how the neighborhood looked in the late 1800's & early 1900's. Average meal per person (no alcohol) = $15-20.
Near your hotel, there are dozens of bars to enjoy. When it's not crowded with the suit-wearing, post-work, 20-something's, McFadden's is a nice Irish-y bar. Decent food, good selection of beer & alcohol, fun atmosphere. Corner of 42nd & 2nd.
In GCT, Cipriani's (southwest balcony) and Michael Jordan's (northwest balcony) make excellent martinis & allow you to see the Terminal when it's quieter (i.e. after the commuters have gone home). Go after 8pm.
If it's not booked for a private party, try to have drinks at the Campbell Apartment - also accessed from the southwest balcony of GCT. The space was a wealthy man's pied-a-terre in the early decades of the Terminal's existence & it's a sight to see.
Drinks are pricey, in NYC. Expect to pay about $5 for a pint of beer, $8 for a glass of wine, $12 for a mixed drink or martini. Bottles of wine run anywhere from $20 - infinity, but most decent bottles at average restaurants can be had for $30-40.
There are dozens of smaller, wonderful eateries, throughout the city. If you'd like additional suggestions, just make a new post here. I'll keep an eye out for you.