Contact your politicians -- local, State and Federal. If they're anti, identify yourself as a law-abiding gun-owner and tell them you're opposed to restricting the rights of decent citizens over the actions of a few murderous lunatics. If they're pro-2A, express your support. Go sign the petition at Whitehouse.gov. Yeah, you'll probably get put on a list but you know what? You already are.
Don't let our side give away the store. We didn't cause the outrage at Newtown, CT, we didn't shoot up a theater full of people in Aurora, CO and we didn't try to harm innocents at a mall in the Pacific Northwest. I'm a little concerned about what NRA might decide to offer -- because offering any concession (other than tightening up state reporting of mental health data to the NICS system) will be taken as an admission of culpability.
A specific model of gun didn't, either. An idiot commenting at NRA's Facebook page (it's back, BTW) asserted "if all she'd [the killer's mother] had was a six-shooter and a hunting rifle, he'd've done a lot less damage." Unlikely. Bolt-action hunting rifles (to chose a restrictive example), even single-shot ones, can be loaded and shot nearly as quickly as you can work the bolt; a lever-action hunting rifle would be slightly faster. Most hunting cartridges are more powerful than the "intermediate" sized .223. -- It is an unfortunate, stomach-churning truth that it doesn't take much power and cycle speed for even a skinny adult to shoot children at close range. On the six-gun side, it appears that the only person the killer at Newton shot with a handgun was himself -- for which even a single-shot gun would have been sufficient. The original "Assault Weapons" Ban proved that banning rifles based on cosmetic features does nothing; the Columbine massacre took place during the AWB.
Realize that these terrible crimes are copycat suicides. That means the longer the media coverage goes on, the more likelihood we may see another successful mass-killing attempt by a deranged young madman. (And I think they know it.) If we are very, very lucky, the attempts will get the same reaction from ordinary people that attempted airliner hijackings do since 11 September 2001, as their intended victims grasp that they have nothing more to lose than is already at risk. More and more schools are teaching students, especially older ones, ways to oppose a killer; the first time one of these attention-seekers goes down under a hail to thrown textbooks (etc.) will be the beginning of the end of the trend.
Know the facts. Know the "official facts" even if you choose to doubt them -- and get expert advice. The "rifle found in a car" was contentious issue here at Roseholme Cottage, until Tam found video of it being removed: it's a scary, black...
Don't overreact. Too much too soon -- I fret over some of the more-tripwired Threepers, despite valuing them as "canaries" -- only plays into the hands of our opponents. (Is this a subjective, tricky, nuanced game? Yes; and that sucks. Remember the stakes!)
Know your audience. In my blog, I can talk about the deterrent effect of removing legal barriers to teachers and school employees being armed if they chose to be (and qualify for whatever carry permit their state offers!). In the lunchroom at work, not so much. Don't be That Guy; we can't afford it just now.
Do what you can, as you can, when you can. Remember, self-defense is a basic human right; surrendering it makes society less safe. And keep after those politicians!
* I'm number 42,398. There were a hundred more signers in the few minutes it took to write about it.