Fireworks build the host's rating, but they don't do our cause any good. So no matter what, stay cool under pressure. Listen to the callers who come ahead of you. Maybe you'll have something to say to support a comment by a pro-gun caller, or to refute a comment from an anti. Never engage in name-calling with the host or another caller, even if they start it.
Some shows are limited to a specific subject, usually related to the show's guest.
On a specific subject show, you of course have to confine your comments to that day's subject matter. The host solicits call-ins to discuss anything they want. You can often get a lively discussion going about gun control. If you bring up the gun issue and the host of an open forum show doesn't want to talk about it, don't take it personally. The gun debate gets a lot of exposure on talk radio, and some hosts may think that they need to force a broader variety of topics.