I have large knuckles, so my college ring spins. I saw a 4-star product on Amazon called a "RinGuard." I was leery of paying for something I wasn't sure would work, so I made this to see if I at least liked the concept. This solution won't work for everyone (downsizes my ring a lot, isn't all that attractive), but it works well for me - comfortable, keeps my ring from spinning and isn't a problem when my hand gets wet. I was also surprised that the ends I heat set with a hair dryer have so far stayed in position.
If I'd had to downsize my ring less than I did, I might have tried flattening the side of the coil that faces my hand. I also thought about serial layers of heat shrink tubing.