People will give you the spiel about “Avoid all eye contact” and “Don’t look like a tourist” it’s kind of true and it kind of isn’t. The only way you’ll look like a New Yorker is if you’re in a hurry to get somewhere, which is stupid for a vacation. That’s probably the number one trait for blending in, be in a hurry. You don’t actually get like that until you have travelled back and forth from work or wherever a few times to actually be able to do it correctly.
The subway will be hell with a lot of bags. Secondly, Penn station is on the west side, so it’d be difficult to get over to Park Ave. and 49th (?). It would involve at least one transfer. Save yourself the grief and get a cab, it won’t be more than 15 dollars.
Having never been in a big city before, be prepared for a shock! New York is probably the crazy-busiest city (Manhattan at least) of any I’ve ever been in. I’ve been in large cities in Europe too, but it’s not the same. It’ll hit you like a ton of bricks when you leave Penn Station (which is underground). It took me a few days to adjust to the pace the first time I came here.
Stuff to see? There’s tons to check out, all of it’s okay. My favorite of all of the touristy things is Grand Central. Don’t know why…
But yeah you won’t be able to not look like a tourist, just try to stand out of the way when you stand still on sidewalks. But regardless of anything you do, people are used to the worst tourists here anyway, so nobody will say anything if you do.
I’ll second the thing about giving directions. New Yorkers love to be asked for advice. Things are also less dangerous than they may seem. A lot of people take cabs everywhere because they’re afraid of the subway. That’s really not necessary…
One important thing to note. If you get on a subway car with someone who is talking to themselves, (probably a drunken bum), do yourself a favor and switch to another car at the next stop. Better to do that than trying to ignore him the whole time.
Also, don’t be afraid of Brooklyn and Queens. A lot of places there are actually more laid back than in Manhattan. All of the crazies tend to hang out in Manhattan, more so than residential areas of Brooklyn, in my experience.