I hope you never have a child if you don't intend to teach them about fire, electrical outlets,
guns, traffic, and other ways they can hurt themselves well before they are 7 or 8.
To answer the question, you teach them about guns as soon as their is any possibility that
they might encounter one, or if they start showing an interest such as doing the "point your
finger, say bang" thing. By the time they can walk you need to start educating them about
anything in the house can be dangerous, so if you have guns in the house, that's when
you start educating them about guns. If you don't own guns and neither does anyone
else who cares for the child, you might safely wait until they start riding their bike to a
friend's house except that by that time they'll be getting miseducated by TV, movies
and perhaps video games. A responsible parent will at least take a few seconds to
say something when the child is watching a show that might leave a false impression.
The "Eddie Eagle" program is the most highly regarded programs for teaching children.
It has material for ages 4-8. Basically it teaches kids in this age range that real people
don't get three lives before they have to hit the reset button, so if they encounter a gun
they should stop, don't touch, move away, and tell an adult.
More information on the Eddie Eagle program can be found at:
http://www.nrahq.org/safety/eddie/
Gun safety information for parents:
http://www.nrahq.org/safety/eddie/
Other safety programs by the National Rifle Association:
http://www.nrahq.org/safety/
Note that while in many people's minds the NRA is commonly associated with it's sister
organization's fifth second amendment work, there are actually two seperate organizations
and the NRA itself has safety as one of it's primary concerns and in fact even the political
repeatedly supported legistlation regarding gun safety, so don't think the NRA is just all
about preserving our rights without any other concerns.