I've been thinking about this in recent months, and with all the Tom Holmoe talk maybe it is a good time to post it.
The most important thing an AD does is hire coaches. Find someone who can get good coaches and the department pretty much runs itself. Donors will come lined up with wallets open. Fans will fill stadiums.
Good coaches = lots of wins & no scandals
Sure there is more, but nothing is more important than the coaching hires, IMO.