Over my left forefinger, under the middle finger, over the ring finger, under the pinky. No wraps around anything. If I want to tighten the tension I just press the pinky down on the yarn. If I want to loosen it, I just lift it a bit.
If the yarn is heavy or sticky, it just goes over the forefinger and across the palm, with all the other fingers curled in a relaxed position over it.