The above listed ways are good, but just keep in mind when reading a book like the Blue Book of Gun Values the actual condition. I have seen many people who think that they have a perfect condition firearms, when in truth they have a 70% condition firearm. Additionally those avenues, as just about every buyer, cares less about the story of the firearm and do not care about sentimental value. Also something is only really worth what another person will pay for it.