Lay down the “house rules:” Situations will undoubtedly arise that require you to correct your visitor’s behavior. Rather than simply reprimanding him, says Wilford, remember that the rules may be different in his house and that he needs to understand the reasoning behind your requests. Instead of saying, “Don’t eat in there!” for instance, say, “We only eat in the kitchen at our house.” If he’s running down the stairs, say “Those stairs are slippery, so please walk carefully on them.” This cuts down on the reprimands while still keeping the kids in line
Let kids work out their own problems: If the children don’t see eye-to-eye on something, resist the urge jump in right away. Small disagreements seldom last long, and if you hang back you’ll often find that the kids work out their own resolution
Intervene rarely, but firmly: If, however, a conflict is escalating into put-downs or physical confrontation, it’s time to step in. Remain calm and make firm statements like, “I can’t let you do that to Natalie.” Remind both parties that words and actions that hurt are not acceptable, and then coach the kids on coming up with a compromise to the original problem. If the fighting continues, separate the children for a while or introduce a new activity that’s less likely to cause conflict.