As with razors, I think it's one of those things where the more you see the easier it gets. Looking at photos of known hones online can be helpful, but seeing them in person is even better. You could dig through the Hones section and the rest of the forum to start to get an idea of what various hones look like and what their distinguishing characteristics are, and if you have someone local that would be even better. But, keep in mind that antique shop and ebay stones are often covered in stuff, and unless you are looking at a clean hone, identification can be very difficult.