Actually the best contextually correct description I have read, consistent with the contemporaneous writings, is that "well regulated" meant to work correctly as in a "well regulated" clock. In that context I prefer to refer to Justice Joseph Story who wrote in his Commentaries on the Constitution:
"...The right of the citizens to keep, and bear arms has justly been considered, as the palladium of the liberties of a republic; since it offers a strong moral check against the usurpation and arbitrary power of rulers ; and will generally, even if these are successful in the first instance, enable the people to resist, and triumph over them. And yet, though this truth would seem so clear, and the importance of a well regulated militia would seem so undeniable, it cannot be disguised, that among the American people there is a growing indifference to any system of militia discipline, and a strong disposition, from a sense of its burthens, to be rid of all regulations.
... There is certainly no small danger, that indifference may lead to disgust, and disgust to contempt; and thus gradually undermine all the protection intended by this clause of our national bill of rights."
Urge your congress critters to start requiring firearms safety training in middle schools, and demonstration of marksmanship before graduation and ascension to the unorganized militia (USC 10, 246 b. 2.).
