The most important thing to make sure your kids are safe is to talk to them.
Ask a lot of questions and know what's going on in their lives.
If you have firearms in your home, make sure they are either locked in a gun safe or have safety locks on them.
It's also a good idea to keep your ammunition separate from your weapons.
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Handgun Safety Locks: Protecting Our Children
Source: http://www.usdoj.gov/ag/gndrgfre.htm (U.S. Department of Justice).