I can only hope that things are different where you're going than they are here, but:
1 - Definitely lay low at first, get an idea of how things work and what to look out for. Ask your partners. Be extremely happy that you have partners, and look out for each other.
2 - Be a doctor first. If you're not doing that, you're doing it wrong. It's not that you can't be an officer, and you should be if you want to stay in the service, but that comes second. Unless you're extremely unlucky (as I was) you won't have to decide one way or another in any significant way, but there will be little things.
3- There are three kinds of people in your hospital: Those that want to help you take care of patients (directly or indirectly), Those that say they want to take care of patients, but really just want the paperwork to reflect that patients are being cared for, and background noise. During that initial period, do your best to figure out who is who because it will make it easier to do your job in the future. Sometimes the first two types of people are doing the same job, and sometimes they're not.
4 - Spend time with your family. You just stopped being a resident. It is very important that you metamorphosize into a physician which requires that you put your head down and work, but at the same time you are going to have more free time. At some point you have to decide whether you're going to be the type of doc who is his work, or the type of doc who is happy. It's a balancing act at first because that first year out is a doozy, but don't neglect your family.
5 - Finally, unless you're going to a major MEDCEN with a lot of support, realize that you have your limits. Its difficult going from residency where you basically accept everything to going into a practice where there are some things you definitely should be attempting. There is an addage that the first time you send something out will be the last time you treat it. There is some truth to that, because you start to lose comfortability. At the same time, you'll definitely be uncomfortable dealing with something if you have a major complication because either you or your facility was unprepared for it. This is an especially significant issue in military medicine, where a lot of the smaller MEDCENS simply don't have the capability to deal with morbid conditions. I recall a patient that I discussed with a pediatrician at my SCEN ($#!T-CEN). She was seeing an 18 month old child for FTT. He had some genetic disorder that I had to look up. He had a trach due to stenosis from prolonged intubation and a PEG for his dysphagia and he had a history of recurrent aspiration pneumonia. She wanted to know if I would evaluate him for decannulation. In residency, I wouldn't have even thought about it. No big deal. And if everything went well, we could have handled it here, too. But if things didn't go well, that kid would have died here. It's not that I can't trach a kid - or re-trach a kid - if need be. It's that 1: they haven't done a pedi trach here in probably ever, 2: the nurses have no idea how to start a pediatric iv, let alone listen for early warning signs or run a pediatric code (yes, they're certified to do so, but that ain't the same thing), 3: we have no ICU let alone a pediatric ICU to ventilate the kid when he aspirates and desats. So for me, it was a no brainer that this kid needed sent out and that he probably shouldn't have been stationed here in the fist place. Take home point: know not just your limits, but the limits of your facility. BTW, I got an ear full for sending that kid out. Command couldn't understand how I could be credendialed to work with pediatric patients, but couldn't treat this kid....Go back to the second type of person in part 3 above...