I think the number one thing is to make sure you have a good battery and learn how to keep it healthy (If you get a used camper, check the specific gravity of each cell to make sure the battery is healthy). You can kill a new battery very quickly by excessive discharging. Assuming you have lead acid, don’t let it get below 50% (don’t believe claims that you can go below 12V). Ideally, get a battery monitor like the Bogart Trimetric. This device actually counts the amps into and out of the battery so you know the state of charge. If you plug in all the time, this is less of a concern, but even then you have to make sure that you get a full charge before and after camping off grid. Your camper likely has a converter/charger that can be very slow to provide a full charge. Check out Mike’s article on the Progressive Dynamics charger install for more info on that. Installing solar would also address this problem (assuming you get a quality 4 stage charge controller). Also check the battery when the camper is in storage. Phantom loads and battery self discharge will make periodic recharging necessary.
Do a test campout in the driveway to make sure you know how to operate all the camper systems and that everything works. Spending a few nights in the camper may also identify some modifications that would make your trip more comfortable. Especially if you heading out for a big trip right away. For example, some of my modifications:
I removed the bathroom door on my Palomino pop-up. Since it’s a pop-up camper, the door didn’t provide any privacy and was really annoying and in the way.
I also just removed the dinette table since it was a joke in a camper that small. And the table and support pole needed to be stored somewhere when you weren’t using it. We found it better to just leave it at home.
Good luck and let us know how it goes!