Most folks would say with solid bend, but don't break, defense, along with a strong running game that would grind the opposition into the turf to the point where they would be utterly demoralized and too darn tired to care.
I'll start with this:
There were many games where we'd utterly crush the opposition, but in my opinion, one of the finest examples of Holtz Ball was against Penn State in 1989, where that team had NFL players all along both sides of their team, especially on their defensive side.
We ran for over 400 yards that game, and Tony Rice put on the perfect exhibition on how to run the option against one of the finest defenses in the nation. There was nothing fancy about the offense that game, just hard charging, run-heavy offense that made Penn State's vaunted defense sucking wind by the 4th quarter.
That was a Penn State team that had Blair Thomas on that squad (and many other NFL folks), and we stifled their running game.
Everyone was running with synchronicity that game, and had we kept that same level of synchronicity the next week, that Miami game wouldn't have turned out that way.
Seeing Joe Paterno that disappointed and demoralized made my day.
If anything, this was a dramatic contrast to the game against Navy in 1991, where Rick Mirer threw for over 300 yards, and the line did a fine job of pass protection, while doing a substandard job of run blocking. He and Joe Moore tore into the offensive line after that game...
Link: For your enjoyment