I don't have a set formula for how to design the ear wire for each earring. But I do always go through the step of consciously deciding what style ear wire suits a design, rather than always having the same ear wire for all of my earrings. If the earring style is large or busy I tend to have a plain or smaller ear wire. You can easily vary the style by using different sized mandrels to create the main round shape. Or you can make them more angular and dramatic. You can try drawing different ear wire ideas, or experimenting with some inexpensive craft wire can give you an idea of different possibilities and is a lot of fun.