dont be a "nuke" like me, this sh!t blows!!!! But other than that know there will be crappy days and good days and know that the crappy ones suck but the good ones always make it worth it!!!!
I work in IT. Been doing infrastructure stuff(server architecture, VM, AD, etc) the past few years. Just moved into the Business Intelligence/Analytics field a couple months ago.
Before you join, research the job you want (get like a top 5). when you get to your recruiting station they'll tell you only such and such job is available. alot of people get screwed over like that. deny that shht and tell them to call you when the jobs you want are available. DO NOT JOIN AS UNDESIGNATED. if you plan to get out after 4 years you might want to get a job that transfers well into the civilian world such as IT or AirTraffic Controller for example. Ship life isn't the most fun, but when you get to port its worth it (or you could get shore duty).
theres so many things i could tell you but the most important is pick your job wisely as you'll be doing it for 4-6 years depending on the contract. or you could go reserve instead of active.
I work at a top 20 course in Florid aas a bartender and a Pro shop worker during the school year. During the summer I work at a different course along with a gas station. Little jobs to make money for school.