Definitely turn off water at the pedestal when leaving.
Checking the power polarity and voltage before hooking up is a good idea BUT, it will not tell you what happens once a load is applied to the power source.
Your refrigerator info will tell you about leveling. I believe mine says up to 6 degrees off of level is OK, Yours may be different.
If you have wet cell batteries, your fluid level will go down especially in hot weather. If your charging system is set too high, this will also cause some of your fluid to be boiled off. Until you know what is normal for your coach, just check the water level every week or so to see how the level changes on your coach.