Never, never, ever walk through an occupied site that is not yours or a friend who has invited you.
Even if you have to detour around five other sites or RV's or walk an extra hundred yards to get to the bathroom, the camp store, pool, river, whatever - never take a short-cut through another camper's site. This is probably the most widespread and accepted rule of RVing worldwide. Be doubly sure you stress this to your kids. This means no bike riding, no walking, and not even any playing on the very edges of someone else's site. Privacy in modern day campgrounds is difficult at best in some cases, so the unspoken, but much noticed rule applies: Know the boundaries of your site and others and respect them.
Even though you're outdoors, use your indoor voice. Voices travel and it's no fun sitting outside trying to enjoy the peace and quiet while trying to ignore the loud conversations of your neighbors. Keep your voices low. If you must argue, take it inside. If you are traveling with children, instruct them to keep their noise down - and preferably on the campground playground or pool.