Seeding meetings crack me up. They always have.

Head-to-head is a wash. If you won you get the seed. If there are multiple matches it's best record. If you split, you could argue last outcome or flip a coin. Either way is fine.
Common opponent is a dumb form of criteria. It just is. The problem with it is that it opens the door for any combination of common-opponent scenario. I have heard arguments like: "Well, my kid, beat a kid in a summer tournament two years ago that beat your kid." Dumb as that sounds, it actually worked!

You take two coaches arguing for a seed -- say second or third at Regionals. Both have 30 wins, both are studs. But all of a sudden, this surly little third coach over there goes, "Um, who are your losses to?" Pretty soon he's arguing that his kid with an 11-21 record beat a kid that gave one of those two 30-win kids a loss. Not withstanding the fact that the common opponent was ahead 14-2 at the time and the surly little coach's kid happened to catch him with a throw or something. Next thing you know you have an 11-21 kid seeded second at Regionals. That's just wrong.

Here's my favorite Regional seeding meeting story. One year, I had a kid in the middle weights was clearly the fourth seed; 20 wins, quality wins, whole thing. Another coach asked for our losses. I rattled them off; all quality kids. The other coach says, "Well, my kid beat 'Smith' (fake name) in a dual." 'Smith' was our league champion, ranked in 4A, but I knew he a couple of losses here and there. And the other coach was well-respected so I didn't dispute it; his kid was a sophomore and had a .500 record and ended up being pretty good. My kid ended up in a draw that had him seeded 7th.

But it didn't make any sense how this kid beat 'Smith,' so on the day between the seeding meeting and Regionals, I called 'Smith's' coach and asked him about it. To my surprise, he told me 'Smith' didn't wrestle that night. He had weighed-in, but during the day there was a death in his family and they took off to travel. Unfortunately, the coach who brought this up at the Regional meeting had his manager fill out the scorebook based on the weigh-in sheets. There ended up being a JV kid in that spot.

So, I ended up calling the other coach and the Regional tournament manager and we ended up redrawing the weight on Friday. No harm, no foul, but if common opponent was not a factor, this kind of crap wouldn't have happened.