When I make a power ranking, I use strength of schedule, wins/loss, situation, and points for/points against. Then I will calculate a home field advantage (based on situation) and create my number for the game. Then I will check my work against 3 reputable sources. Personally I use Statfox, and a couple of professionals that I follow...if there are any discrepancies greater than a half point (1/2) to a point and a half (1 1/2) then I will look into the situation to find out "why"....from there I'll take a look at board and see where I can find some value...for NFL I'll look on Sunday night, Monday morning...if there is some early value I'll bet the game and wait to see where the line goes...sometime I'll get a good middle...sometimes I'll miss....then look again at the end of the week....finally I'll check the lines on game day and see how far the line moves....from steam or pubic bettors...some times there you can beat the closing number.