Whatever method you use, be careful. That is the main concern.
I, personally, have seen more people smacked in the head when their stringer broke or slipped off the bow limb. I've also seen hundreds of older bows with twisted limbs and the majority were from improper storage (left strung or stood up in a corner somewhere).
Bow stringers are kind of like safety harnesses. A lot of the hype and the horror stories are fueled by the sellers of those products.