A handy trick to have in case you have a drop while juggling rings. Fair warning, this can be a little hard on your finger, so take it easy as you practice.
If you want a bit more on single ring spins, check out this tutorial.
Tips/Hints: The biggest key to success is making sure the two rings are separated when you start the spin.
You'll need a strong start to keep them spinning, so whip your hand back like you mean it.