Any supporters can sign the petition, not just regulars that go to the range. We're trying to get to at least 2,000. More the better. 10,000 would be great.
Family members, friends, co-workers, acquaintances, classmates, roommates, other organizations (sierra club, boy scouts, etc)... If you're sitting around doing nothing, talk to the guy next to you and have them sign it on a smartphone.
On the petition page, click the "Post to Facebook" or other links buttons and spread the word.
Not sure if there's a minimum age for petitions. Anyone know?