My kids are 7, 9, and 11 now. It's really hard, but here's what worked for me. You have to teach your kids the only things they can play with is their own toys, nothing else. If they want to touch or use anything else, they must ask first. They have to learn to respect what's not theirs and leave it alone. As I said, not an easy task. The upside is obvious, but one of the benefits is you can take your kids anywhere (including friends houses) and know they won't end up causing a problem. Childproofing your house is easier, but does not address the fundamental issue. The kids get older and more responsible but the nature of the challenge shifts and make being vigilant even more important. A good example is the internet, they cannot be allowed free reign to do what they want, there has to be some supervision. Am I an overprotective parent? Nope, but the inmates can't rule the cellblock either.