When done right, rings can be a sick addition, turning a good outfit into a great outfit. The warrior poet Beyoncé once said "If you liked it, then you should have put a ring on it," and she was right.
Rings are one of the few pieces of men's jewelry that don't have some kind of practical usage — unless you're a Green Lantern, of course. Tie clips, watches and belt buckles are all there for a reason, but rings should either be fun, or carry some serious emotional weight.
Outside of never wearing them on your wedding finger (left hand, third finger) without good reason, there aren't many rules when it comes to rings. A maximum of three per hand is probably worth sticking to but within that you can mix and match. Boom!