It's pretty basic sounding, but...
I cleaned up the frame to ground connector on the body first. Then added a ground wire that attaches to that and to one of the heads, then another that attaches from that point to the other head. It was amazing to me how much my idle smoothed out at the time, and my headlights got brighter. Got the ground wires at the local Pep boys. I routed it between the idler pulleys, but a longer length can get to the front engine mount/coil holder, which also goes into the head.