Begin by demonstrating the safe handling of firearms, checking to see if your gun is unloaded, keeping the action open and storing the firearm responsibly. Any child that views these behaviors over and over again will be on the road to good judgment of firearm safety, and respect as they mature.
That's a good start, but enroll them in programs to further that respect. A great starting point is 4-H Shooting Sports. Youth 8 to 18 can participate in a hands-on learning experience about firearm safety, proficiency and competition. There are disciplines for air rifles, air handguns, .22 LR rifles, .22 LR handguns, shotgun shooting sports, muzzleloaders and archery.
The Boy Scouts of America also promote firearm safety and participation in camp settings, and weekly programs. Youth receive badges for their experience and course instruction combined with shooting events.
Conservation organizations like the National Wild Turkey Federation offer youth firearm programs. The JAKES Takes Aim program introduces and educates youth 17 and younger in shooting sports including air gun target shooting and clay shooting sports that are oftentimes hosted in conjunction with local shooting facilities.
If you're searching for youth programs in your zip code, visit websites such as the National Shooting Sports Foundation or the National Rifle Association. They host links to youth shooting programs, information, funding and assistance to start a youth program in your community. Organizations like those noted above realize that shooting sports can be as important as ball sports in molding youth into responsible, firearm-respecting adults.
For more info on NSSF's Project Child Safe go to ProjectChildSafe.org.