introducing a 12yo to firearms. . . .

[Hawaiian]

Lot's of good advice already given. The one thing that I did not learn as a kid or even as an adult when I first started shooting, (I am old and that was a long time ago), was to never never place you finger inside the trigger guard or touch the trigger until you are aiming at your target and ready to shoot. Without training in this the natural or common practice is to pick up a gun and place your finger on the trigger. This is how most accidental shooting happen. While all of the safe handling rules are great, this one takes some practice to overcome the habit of handling a firearm this way.
That said, buy him a BB gun and teach him safe gun handling with it first. Then you will know when he is ready to move on to a real gun. Tell him that he needs to listen to you and learn how to safely handle his BB gun and only after he has shown that he can safely handle the BB gun will he be allowed to handle and fire a real gun. This gives him an incentive.

 

[FreakyStylie]

I took all of my education for granted, and now I'm in the a similar situation . . . training my 11 year old about safety. When I went to school, we had requirements in junior high. All boys and girls had to take all of the following courses: cooking, sewing, wood shop, and hunter safety. We shot CO2 rifles in class and were well trained in the proper handling of firearms and everything related to them for half of a school year.

I just pulled out my rifles for him to see a couple days ago. There was just a little too much excitement in his eyes for my comfort level. Our first outing will probably involve him watching me, while he is controlling the muzzle of a stick.