You leave the whole ear on when skinning, just cut through it at meat level. If you're stretching the hide to sell, that's all you need to do to it. If it's being tanned or mounted, you need to get the cartilage out, which is a lot easier to do after it's skinned. You basically turn the ear inside out. Taxidermists use a special tool that looks like a smalll shoe stretcher on deer and bigger critters to pop the skin loose from the cartilage. You can use the end of an old spoon handle or something similar on smaller critters.