I traveled to New York and lived there on and off from the age of 19, considering i knew nothing about 'The big apple' as its affectionately known, and i was only a young lass, I had to figure out a whole lot on my own. I'm writing this in basic form, just so you can get to grips with the place as soon as possible.
First things first, yes it seems scary just packing up a bag and going but don't be scared, New York is a place where anyone on the street will help you. I arrived with a backpack and a bit of money, no where to stay at all!
So here it goes.

*BOOKING
-Book with Delta airlines. They are cheaper and just as comfortable than most of them, not as cheap as air India but I flew with Air India to NYC once and they were TERRIBLE. The Airplane stank, it was dirty, food was sickening and gave me the runs, and they renew your flights and alter them by FAX???? hello it's not 1985
-Go on www.hostelworld.com and pay a deposit online, you pay in full when you leave. It's cheaper to do this online. I got a room for $10 a night and it was lovely. Any Jazz on the city hostel is perfect. I stayed on Amsterdam avenue on the upper West side, nice people, safe, clean, en-suite bathroom and parties on the rooftop.
-I used a hostel but moved into an apartment using http://www.craigslist.org/about/sites you can find roommates or info about apartments that are going cheap for the month. If you want my advice DO NOT PAY BEFOREHAND you might get robbed, I payed ont he spot when i got there, some crooks ask you to pay over paypal and then disappear. I got a nice converted warehouse in a safe part of Harlem for $250 a month.
-Make sure you have an HSBC account as there are literally tons of the branches in Manhattan so you wont be charged if you need to withdraw cash and if you lose your card you can withdraw with I.D.

*TIPPING AND TAX
-Remember 10% if you liked your meal/service OR 20% if you were really happy. Note this is for everything! manicures, taxis, waitressing, everything!
-If you see an item of clothing that wont be the price on the label, you will have to pay extra tax or vat on the counter when you pay, so don't think your necessarily getting a bargain

*GETTING AROUND
-Firstly....Don't freak out at how big the place is, just remember it's all on a grid of squares, its not like england. There are no alleys or winding roads, its literally blocks so you can always find your way again if you get lost. Think Packman but bigger.
-Buy a decent map of NYC including brooklyn and Harlem, they usually have all subway maps and tourist attractions on them. You can get the really good ones at the tacky tourist shops surprisingly. If you have an i-phone or are near a wifi spot check out hopstop.com, type in your current location and where you need to be and it plans a journey by subway, bus or walking, most people new to New York use it.
-The public transport is amazing in NYC, you can set your watch by it and its cheap as chips.
-Go to any subway and get a 2 week or 4 week pass they are really cheap. A 2 week pass is only about $25 and you can use it as many times as you want, peak or no peak. Make sure you have the cash as you can not use your card. I also advise that you buy one of those small hand-fans and a bottle of water before using the subway, I cant describe how hot and airless it is down there. I once laid on the ground and my friend fanned me with a newspaper. On the plus side, the carriages are super cold and refreshing.
-The bus service accepts the rail cards but try to avoid the bus, as some rough types are likely to get on them.
-If you go to the greyhound coach website or go to a station and enquire, you can get to New Jersey, Conneticuit, and if you can stand sitting long for journeys, you can go further afield for next to nothing. There are also ferries that go out to Rhode Island.
-Avoid cabs, you really shouldn't have to get one, I never did, they charge WAY too much and take you the the long routes to get more cash, you also have to tip them.

*SHOPPING!!!!
-Well firstly bargains and unique clothes
-For you guys we know you love your rare Nike dunks and snazzy tshirts so I have to say get yourself to Dr J's in Manhattan! I got some limited editions that are worth £150 for a mere $50! also try to get to a store called Yellow Rat Bastard 483 Broadway for some real finds. That street in general is brilliant for one offs and bargains. Really good food too.
-Manhattan mall is pretty small but stocks big names at low prices, its located near the Pennsylvania Hotel. Macys is great and stocks affordable and not so affordable clothes from Ed Hardy to D&G Its a good mix of prices. If your ready to splurge then Bloomingdales and the designer boutiques down 5th Avenue are for you!
-If you're a bit of a magpie then look up some of the thrift stores and vintage sales that are dotted all over brooklyn and on occasion the east village, you will have to hunt though, as they are never in one spot. Try and get online.
-If you are starting to feel all disheveled and untidy you can get a manicure and pedicure for around $15-25 and a haircut for around $20-25 so it's cheap and let me tell you the ladies in NYC do not leave the house without their feet and nails done, it's law there! I always went to Brooklyn or Amsterdam avenue, you can get a manicure even cheaper in chinatown but i thought they were a little frosty with me and i felt uncomfortable. If you go into Manhattan your talking a lot more.

*AVOID AVOID AVOID!!!! (because of the terms of this article, I must state these are my opinions)
-Try not to go to the East side of Harlem, the west side is pretty safe, i lived on Lennox and never felt unsafe.
-Avoid the Bronx at all costs you are not going to be safe or welcome there especially if your'e a tourist. There is a race issue in some parts, I was welcomed, but there is a white/Black divide in some parts and you will find that your reception varies.
-Don't ride the subway on your own after 12pm, take a cab if it's a short distance. There are some real strange characters that can make you feel unsafe. Also don't give money to the beggars on the subway, the more you give the longer they stay, a lot of them aren't even homeless.
-Try not to eat food from the general stores that sell cigarettes and beer. It's left for days and reheated.