The scope of this discussion is strictly options or suggestions on HOW to create policy and law and how to implement them in the US so as to reduce the number of guns in the hands of those who intend to use them for criminal purposes.
Whether or not those options should be explored is not under debate. The 2nd Amendment is not under debate nor under discussion. The assumption of the thread is that "gun control" law is necessary at this point and which policies and laws are good to pursue on the basis of putative results.
Foreigner speaking here. I'm Filipino. I have never been to the US, though I do have friends and family who are Americans.
First suggestions to kick things off:
All anti-personnel firearm weaponry will be illegal outside of police uses and police stations. To accommodate sport shooters, local stations will have ranges and armories that will house guns for sport shooting. Police will be present when these guns are in use. They are to be checked in and checked out, all accounted for, including ammunition.
All guns are to be registered to either owners or sellers. Owners and/or sellers will have Strict Liabilities whenever any one of their registered firearms is used in a crime. These are civil liabilities covering damages and medical bills.