Navy vet here.
Always wear hearing protection, double if you're around planes taking off. Even if people call you a faggot. You will be wearing a hearing aid when you are 45 if you don't.
Go to medical for everything you have. You are not a "tough" guy if you suck it up.
Get medical shit documented--everything. When you get out, you need this shit documented to file a VA compensation claim--occasionally called VA disability.
IBS due to shitty food and stress, you can be compensated $400+ a month for IBS alone.
Knee surgery, sleep apnea, tinnitus (make sure you go to the doctor and say you have ringing in your ears when you are in)-- this alone gives you 10% VA compensation.
When you have a successful VA comp claim, you are considered a disabled vet as far as the VA home loan is concerned. This makes you exempt from the VA funding fee and private mortgage insurance.
GO to medical for fucking everything. You will be asked to do shit which a "normal" person would never have to do. Your will get fucked up, you might get depression, you might get any number of things.
When you get out and file the va comp claim, they look for conditions caused or exacerbated by military service. Some if you have something now, and it gets worse, you might get paid.
When you get out, the DAV will help you with your claim.
Don't be a retard and smoke pot--it's the only thing I've seen people pop on a drug test on--you will get an OTH discharge, which isn't bad persay, but with an OTH, you have to prove that your service was honorable to the VA to get certain benefits, which can be done, it's just a pain.
Don't throw people under the bus to make yourself look better--stand out on your own merit and character.
Don't drive drunk.
Don't do dumb shit some faggot can send you to NJT for, like fucking someone elses wife or getting in fights on base..