I used about 24 inches of string for my necklace. At about 12 inches, I wrapped the cord around the base of the pine cone making sure it gets into the "scales" and tied a knot. I embellished my necklace with beads and mini tassels. These would make great earrings as well. Your pine cone jewelry would probably last longer if you give it a coat of clear nail polish or clear spray.
Hope your friends will be pining over your new necklace this holiday season.