KB
Rifles and semi-auto pistols
1) Point the muzzle of the thing at the ground
2) Remove the magazine
3) Cycle the action 6 times
4) Look in the chamber to ensure that there is not a round stuck in the barrel
5) Remove the bolt/breach block
Lever actions
1) Empty the magazine
2) Cycle the action 6 times
3) Hold the action open and check that there are no rounds in the chamber
4) Close the action, lower the hammer and put the safety on
Revolvers
1) Drop all rounds out of the cylinder
2) Remove the cylinder
Shotguns
1) Never come across one that could not be broken down (ie pulled apart into 3 bits - barrell(s), stock/trigger assembly, forestock (?))
Hav'em do the above in front of you.
If they refuse - tell'm to walk.
Dr 
PS: If this is a significant issue for you - get good weapons training - not the crappy pay-your-money-and-get-told-the-answers-to-the-exam-you-have-to-do-to-get-a-firearms-safety-training-certificate.
PPS: A highlight of my somewhat inauspicious military career was walking into the UQ branch of the Commonwealth Bank through the middle of an anti-Vietman war rally, with an Owen sub-machine gun tucked under my arm, to collect an army pay-roll!
Amazing how people give you a wide berth when you have one of them things! If they only knew what I knew - IT WASN"T LOADED!