The best way to hang outdoor string lights is by using a light suspension kit. The mistake most people make is using the main power wire to attach as the hanging points. You shouldn't do that since there will be live voltage flowing through that cable, so instead, this kit offers coated wire to attach to the buildings or trees where you want to hang the lights. The lights themselves have hanging hooks or eyes where you can thread the hanging wire through, taking all the tension off the powered wire.