If you are buying at gun shows, I carry with me:
- bore light, chamber gauge, choke gauges, hand loop, tape measure, one of Dean's forend tools. Sometimes I will have a three piece rod in my backpack.
If the bores are dirty or heavily oiled, and I am seriously interested, I will ask to have them wiped.
Look for differences in finish condition. Barrel bluing/browning better than the action colors and or stock?
And then there are the on-line auctions. Any of them. Even with good pictures, much can be hidden.
One of my very early auction buys was a Parker G, with a badly broken stock. Otherwise in good condition, screws, barrels, all functioned, etc. I didn't discover for several weeks when I had time to dissemble the gun, that the firing pins had been ground off.
See Dean's comment about experience!!!