Ok, once you get out of boottcamp, how long does it take before you get assigned a post? Do you pick your own post, or do you just go where you're needed? Whats the day to day life like once you are assigned?
At least for the US Navy, that depends on whether or not your "rate", (what you would call your job) requires you to attend an A school, where I'm currently at for my rate, which is an AB.
You figure out, and if you're lucky, you can pick (good luck picking nowadays though; a lot of people are trying to get in so a lot of people, like myself get handed a job) your job when you first sign up all the way in the recruiting office, and where your A School will be located. A School is usually a few months long, and then you get your permanent duty station out in the Fleet attached to a ship.
You jingle and jangle that in your head all through boot camp; for me, I knew sunny Pensacola (where I'm at right now) would be waiting for me at the end, so that helped keep me going.
Of course you can somehow squeeze through the recruiting office without any job or A School lined up, which means you go immediately out into the Fleet undesignated, until you can find a job. That usually means doing menial work until then, so make sure you have a job and a school lined up before you sign that contract!
As far as how A School is like? Well, there are a few for different jobs throughout the country, but the one in Pensacola is among the biggest, and it's pretty nice here! If you're not in classes/training, you're helping or doing duty in the barracks (which, contrary to your mental image, are more like nice ass apartments rather than STEEL BED/LINOLEUM TILES).
The day to day isn't bad at all; you gotta wake up early, whether its for class or for duty, but everyone's already used to that. You do what you gotta do and usually you get let off at like 2-4 and the day is yours to do whatever; shop, hit the beach, check out the base recreation center for a movie/video games/pool/hang out, hit the gym, or go to your barracks and chill and play video games or computer or whatever.
It's sort of like college, but a military setting and a bit more strict. Think of it like a real life Balamb/Galbadia Garden, no joke. It's pretty nice.
However once you finish training for your job and go out into the Fleet, it's even less strict, you just wake up at your house, do your job at your ship/base, and go home without anyone telling you what to do.