I think it just comes down to respect. If you haggle, do your research, notice the environment, and make a reasonable offer. Don't insult the guys with an offer than even you, if you really stop and think about it, know is too low.
I've haggled on pretty much everything subject wise, but I don't always haggle. I only haggle when the money is tight. And that include big box stores, where i have bought a couple new and used firearms. case in point, i got a pristine Remington 11-87 compact 20 ga for one of the kids. It hadn't even been shot enough to break it in! I got the gun, box of shells, case, original box with all materials for $450. Not the steal of a lifetime, but not bad for a practically new gun.
They need to make a profit, and in the case of my LGS, the guys there are great and have jumped through hoops for me to find some guns and specific ammo.
Keeping all of that in mind, the most you can do is ask. The worst they can say is no, if done with respect. No harm, no foul.
And getting the calls on good deals comes from repeated, long term business you have brought them, where they get to know you and your likes. Don't expect to get a call on anything if you've only been in a couple times and hardly bought anything.
Last edited by globemaster3; January 6, 2013 at 12:05 PM.