One of the ways I use to discuss firearms w/ people who don't necessarily oppose them but aren't enthusiastic about them is to ask them questions.
One of my favorites is to ask them what they thing an "Assault Weapon" is. I have yet to have someone tell me anything other than the usual variations on "High Powered Machineguns" and everyone has been surprised when I inform them of the reality of them and the deliberate attempts to confuse the public on the issue.
Now I've added one more tailored to Illinois residents. I ask them if they think that the Chicago firearm laws are really intended to stop criminals. Then I tell them about Alderman Mell and his Daley approved personal exemption after he forgot to follow the laws.
So how do you discuss the issue w/ those in the middle?