Be sure that you know what sort of engine the beast has. If it’s a gas engine, no problem, you can fill it anywhere. If it’s a diesel, keep that in mind when you’re getting near empty. It’s no fun to run out of fuel because the last place that sells diesel is 25 miles ago.
Speaking of gas stations - look out above! If you’re used to driving a car, you may not be accustomed to watching out for overhangs, canopies, trees, signs and similar things that are at just the right height to clobber an RV.
If you send someone out behind to act as a spotter when you’re parking, go over the basic concepts with them in advance. I’ve seen a lot of times where the person doing the spotting was clueless up until the moment of <crunch> “Hey, you hit the tree!” rather than the far more useful “Hey, you’re about to hit the tree!”
Some refinements in spotting are the commands:
“hold” which means “stop while I check if you’re about to hit that tree” or “hang on, there’s a dog over there that might get in your way, let’s wait for him to move away”
“stop” means STOP! NOW! That dog is about to run under the RV.
Be sure to sort out left/right. Whose? Do you want to move the tail of the RV to the left, or to turn the steering wheel to the left?
It’s also good for the spotter to be able to communicate distance - as in “back up four feet” or “Your bumper is six inches from the brick firepit” rather than “a little more… a little more… <scrape!> too far!”
If you’re on a two-lane highway, be kind and use the turnouts (if the road has them) if there’s a line of cars stacked up behind you.
When leaving a campsite, double-check that everything’s been properly stowed or secured. It can get very expensive if you drive off before raising the stabilizers (frame damage) or disconnecting the electric (damage to the RV park equipment, and to the power cord). It can get very dangerous if you drive off without securing the awning (it flops out on the highway, falls off and hits someone’s car) or don’t latch a storage compartment (stuff falls out onto the road)
Most importantly, have fun!