For a new trailer, my tip would be to be careful to check for loose plumbing fittings causing leaks. I would pressurize the system and open every drawer and cabinet to make sure there are no leaks anywhere.
Last week, with my first trip with my new trailer, I pressurized and quickly started following the plumbing and found a loose fitting behind the sink of the outside kitchen that needed tightening. At that point it was only a very small puddle, but if I hadn't looked it would have leaked all week probably causing a lot of damage.