Hello Kate, after you have formed the "wave", be sure to place the chain nose pliers on the wave wires, about 1mm above the edge of the ring, and then make a firm bend 90° toward the center of the inside of the ring.
When determining how much to trim off, look at the width of the ring as it graduates from thin to wide - cut the wires about 1mm shorter than the width of the ring they are going over (meaning, angle your cutters so that the outer wave wire will be shorter than the one closest to the center). After you give the wire ends their direction with chain nose pliers, use flat nose pliers to push them over the edge and down onto the inside of the ring. When they are where you want them to be, crimp firmly.
After performing these techniques on both sides, to smooth the ends and tighten them closer to the inside of the ring, place the ring on the graduated mandrel and use a screwing motion while working the ring up and down the mandrel. This always works for me!
Answer contributed by Dale "Cougar" Armstrong