When you go to the really good training facilities -- Gunsite, Thunder Ranch, Shootrite, Sig Academy, etc., there is an ethic at work. If you don't handle your gun safely, not only will you be spoken to by the instructors, but you will be viewed by other shooters as someone they don't want to be around.
So, what do you do? First, make sure that you are not "that guy." Your muzzle can never, ever, point at anyone.
You also watch others. No one gets a pass. Speak up the first time you see a safety rule violated, and don't be shy.
Gun safety practices become almost a religion. Make it an integral part of your life, and never deviate from it. Don't be around anyone who does.
from: Tom Gresham's Gun Talk® @http://www.guntalk.com/site.php?cid=877998&pageID=1