Answer:
Most of us use two pair of needle-nose, chain-nose pliers when working with very tiny jump rings, one pair in each hand. Use the pliers in the non-dominant hand to hold the ring on one side of the opening and use the pliers in the dominant hand to open and or close the ring. Pivot the ring to open it-don't try to pry the ring apart sideways, as that will only deform the ring.