There is a formula to it.... Basically it's..,
(2(Opponents winning percentage) + (opponents opponents winning percentage)) / 3
So, basically your opponents winning percentage is two thirds the score, and their opponents winning percentage is a third. For the old BCS calculations, they did not include records for FCS opponents or opponents of opponents.
Consider that inside conference play, one team wins and one team loses every game, so though there a some variations due to who plays who within the league, the majority of the SOS is largely determined by OOC schedules.
So, in our case in 2014, Miami, Akron, and Ohio had net losing records. Unfortunately, they all three did this in by far the weakest division in football which produced 1 team with a winning records and played no one significant OOC, sooner SOS in this logic took a pounding.