Two or maybe three!?
Middle finger in corner of mouth, knuckle of index finger just under and behind my zygomatic arch, and base of thumb just behind my jaw. I don't think aboutmitmas much anymore, it's just where my hand kinda fits now when I'm at full draw.
I used to really concentrate on middle finger in corner of my mouth trying to dig in on a particular tooth, but after watching Terry's form clip in the tradgang video I began to focus more on the "double anchor" and getting my elbow around and now my middle finger is the least component and my thumb base is more prominent if I focus on it.