A compilation of various often useful facts is a good idea. I don't have such facts to offer at present, though I'll try before too long to compile some. Some further thoughts:
I _strongly_ encourage anyone interested in the empirical debate to read _Targeting Guns_ by Kleck. Kleck is very good with critical insight and discussion of methodological issues as well as bringing out helpful facts. He provides a nice review of criminological and medical health literature there. The book is also full of references to and summary of the most important literature for any further reading. (For more on the public health guys see his older _Point Blank_, which is harder to find now.) _Targeting Guns_ is I think the most impressive book on gun control, for or against, there is.
I've had wide-ranging debates on all sorts of topics concerning guns, from the central to the obscure, over long periods of time (well, who hasn't on this board?
). In my experience, the most impressive data to those who are uninformed but anti-self-defense are the self-defense data from Kleck, and all those before him who get less credit. Both the total "X million" survey results and the efficacy of guns vs. other means of defense.
Second in impact is the very low accident rate for guns, as well as the fact that most "gun violence" is suicide.
These two things are impressive in and of themselves, but they also are impactful because they tend to make people realize the extent to which they've been propagandized. It's important not to underestimate this second kind of information. As you all pretty much know, the most obstinate support for gun control comes from ignorance combined with all the media coverage (except in a few recalcitrant cases, anyway). Start to knock off both of these legs and you can do a lot.
Let me just say, by that way, that just about everyone who posts on this board regularly is well-informed and doubtlessly has his or her own techniques in discussion. This is just my experience, and even that has varied a bit. So take it for what it is.
Lott's book, _More Guns, Less Crime_ is pretty good, too; it's just narrower than Kleck's in focus, and less useful against the old "but it would be better if no one had guns" chestnut.
The constitutional arguments I find are limited in their appeal. There is only a narrow range of people, I think, for whom two things are true: (1) they are able to have their minds changed, and (2) the constitutional issue is the dominant factor in their views on gun restrictions.
There are some places where reasonable, informed, and useful discussion can occur on the net: newsgroups other than the gun groups. Groups like the outdoor groups, the hiking groups, the bicycle groups, and (to a lesser extent) travel groups, like alt.culture.alaska. Many people I know said it was a few intelligent replies to "guns in the backcountry", or "guns on bicycles" threads which got them thinking differently about guns and gun control. These rage constantly, by the way, as anyone who lurks in these groups more than a day or two will discover.
Then there are the letters-to-the-editor type things, the importance of which is appreciated by lots and lots of people here already.
Maybe it's worth emphasizing how useful this kind of stuff is, though. The letters that you all write to papers, web sites, newsgroups, or wherever by and large make a very nice impression. They're smart, clear, informed, and reasonable. They make a difference, not just because of what you say but because of the mere fact that you come across in your writing as reasonable, responsible, and informed citizens. That someone who's not a violent, inarticulate misanthrope actually has the opinions you do makes an important impression in and of itself. When you consider the extent to which public education on guns rests almost entirely on the shoulders of people like those on this forum today this becomes even easier to appreciate.
Well, I suppose a good deal of what's in this post won't come as news to many here, but since I typed it I'll just leave it. Maybe it will be helpful to some.