Yeh you get your passport through the PostOffice. You need to fill out the forms have valid identification. Have photos for the passport (specific sizes are needed) that need to be signed by a guarentor who says that you are who you say you are. You also need to allow about a fortnight for the passport to come through cos it has to be processed. And not too sure how much teh passport costs.
I have big issues with taking off/landing. I have smallish ears and it HURTS ALOT for me. So my advice is (if you are indeed allowed to take anything on due to the new restrictions) take chewing gum/mints/something to chew/suck incase your ears hurt also. If youre sucking on a mint or chewing gum it lessens the pain and helps. Don't know why but yeh I was in agony without those things. Since youre going to America this is important cos you will probably have to do alot of Domestic flights over there (I did anyway).
Also make sure you have alot of entertainment for yourself, whether it be magazines, books, those puzzlebooks (i mean seriously i dont like those but some people do), gameboy, etc cos even though there are the movies. You willlll get bored. I'm telling you now. ESPECIALLY if there's someone next to you who decides youre interesting, and theyre.. not.
Um also, if you are flying with an American airline during domestic flights do NOT eat the meals. They are worse then the normally bad airline food, and made my 2 brothers and father (with stomaches of like. i dunno incredible durability) ill.
Additionally, you may not (it affected me and my mum but we have sensitive stomaches) btu you might get sick from a cheese called 'Jack cheese' Americans use it in cheeseburgers (or at least they did) and other meals and I love cheese. But this cheese made me throw up. But my brothers were fine so yeh, just a warning..
Thats all I can think of. Probably not too helpful but yeh. Hope it was.