A jump ring is a circle made of wire that is used to connect components together or to serve as a holder for dangling components. Jump rings are one of the basic building blocks in jewelry making.
To use a jump ring, you must first make the opening wide enough to insert whatever components you are trying to link together. To keep the components in place, you must then close the jump ring. How you open and close your jump ring is important! Doing it the wrong way will distort its shape and, depending on the gauge of the wire, it may also weaken it and make it prone to breaking.
Oh, you may get away with doing it the wrong way a few times and think, “Pish! Posh! It really doesn’t matter!” Trust me, it does. And if you want to make good quality jewelry that will last, you will take this tip to heart.
Figure 1 shows the wrong way to open or close a jump ring (pulling it apart horizontally in a parallel plane). Notice the arrows, which show the direction of the pull.
Not this way!
Figure 2 shows the correct method of gently twisting the cut ends in opposite directions. Actually, you are only going to twist one side away with one set of pliers as you hold the other side stable with a second set of pliers.
Can’t quite see what I mean? Go here and here for two short videos from the Instructables and The Alchemist’s Vessel websites that are much clearer than my typed instructions.
Oh, and remember simple loops from Post 3? This method, and the reasoning behind it, also applies to opening and closing simple loops.
An Earring A Week 
Another tip that is useful is remembering not to open up your jumprings too much. Open it just enough to put together the components of the project you are working on. Sometimes overstretching it can make it a little more difficult to put together, At least it did for me.
Thanks for adding that, SouthEndPhotos. This is particularly true with the larger gauges of wire.