ORIGINAL: The Rev
First of all, I don't use that heavy stringloop material everyone else uses. I use 500 pound parachute cord. It's very small diameter and use only enough to fit your arrow nocked and release. Make sure it's tight, open with a needle nose pliers tight. It will not slip. I don't serve it, or use anything else on it. It will stay in place if tied and set right.
I do the same with mine, and haven't had any problems. Tightening with pliers is the key to this opeartion. I've never needed to serve it in either.