I only have a couple of watch chains, but have seen a few, in shops and pictures and people who had them, also have seen some on the net, if you are interested do a search.
Chains can have a ring that clips to a button, or a "T" bar to go through a button hole, or a clip for a loop (which can go on the waist or on a special loop on a vest), or a clip for a belt, some have two chains, one for the watch and a shorter one for some kind of decoration, (I have one like that from the Mexican railroads), there are also small fobs that go on the watch and hang outside the watch pocket (my uncle who past away earlier this year had one of those, I wonder what was of it), some modern watches have a fob that goes on a belt loop and the watch just hangs from there, not long enough to get to a pocket, there are also leather cases or sheaths that go on the belt and hold the watch in a section that opens and folds away so you can see the time without taking out the watch (I have two of these, also from the Mexican railroads).
You can put something at the other end of a chain (such as a small pocket knife as Dr. Nick does) the watch goes in its special pocket and the other end goes in another, the chain can go across a vest and maybe pass through a button hole.