Not too long ago smoking was an acceptable custom. But today it is not. The change was simple: smoking was made socially unacceptable. It is considered a filthy habit. What facilitated the change? A concentrated attack on smoking on every front. Today smoking is still legal, but seriously frowned upon.
This is the tactics that could and should be made about guns. Keep them legal, but expose them for what they are: means to kill. They have no other reason to exist. If someone wishes to use firearms, let them join the armed forces or the National Guard. It can be argued that they can be used for hunting. So let there be single shot guns or rifles. A hunter does not need automatic or semi-automatic weapons. Better would be using bows and arrows, make hunting truly a sport.
But even this kind of change would not be easy to implement. The solution would be the classrooms. Teach the children what weapons can do. Show them the results of mass murders, the corpses of their friends and classmates. Let them see the blood. Cruel, but useful method to change the attitude toward firearms.