1. Most New Yorkers are pushy, rude, and/or angry. They'll say they're *ahem* "focused." They move quickly unless they have a cell phone, iPhone, or some other goofy gadget glued to their face or hand surfing the internet. If you see any type of communication device in-hand, owner glazed-eyed, avoid them at all costs. All internal navigation systems and notions of their surroundings disappear with the ding of the 3G network.
2. If you see litter on the subway, DO NOT touch it. Good citizens throw away their own coffee cups, newspapers, and Kleenex. Tourists looking for infections discard other people's trash. Unless you have the handy-dandy Purell bottle in your purse or pocket, LEAVE IT. The MTA has people that do that kind of thing armed with latex gloves, face masks and Napalm.
3. You can eat Applebee's and Olive Garden at home, folks. There are hundreds, maybe even THOUSANDS of new, different and exciting restaurants to try in New York City. Even a deli is better than McDonald's. It's often cheaper and faster, too. And here's a news flash: if you're sitting down to a meal, 18% is an adequate tip. 20% if you really enjoy the server. If the guy or girl's OBVIOUSLY an actor, go 25. They're probably broke and the road to stardom can be long and trying. "Double the tax" is a boat that don't float. Unless, of course, you catch your server picking his nose before he serves the bread. Then you roll at 15, not a care in the world.
4. DO NOT stand in the middle of the sidewalk looking around, gawking at a map, or staring straight up in slack-jawed awe of the big buildings. Not everyone in New York City is a tourist. Some people actually have places to go, things to do, and lives to lead. Just because you and your ENORMOUS (and I'm not talkin' number of members, chubby) family from Iowa/Michigan/Oklahoma all piled up in Greyhound to see the big city DOES NOT give you the right to spread out your entire family from building front to curb. Think about the folks trying to pass, please.
5. Hardly anyone who lives in New York is actually FROM New York. So, if someone gives you attitude about being a tourist, ask them where they started. Chances are, it won't be The Empire State. Then tell 'em to go F*$# themselves. You don't get much more New York than that.