How I draw the lines.

Quick way

take tonight's NBA game Utah is at Atlanta. 

Taking the avg of points Utah scores and Atlanta allows gives me 225.2

Again what Utah allows and Atlanta scores 

218.9

Allowing me the avg 114 to 110 game Atlanta at home is plus 7.5 a 3.5 from my determined score.

Hence Atlanta has an advantage to cover the spread.  

The score range is 218 to 225 with over under at 227 then under has an advantage.

Hence Atlanta plus 7.5 and under becomes my bet... again not fool proof and certainly not always accurate but allowing a better than 56 percent win expectancy rate.

What are you asking us dumbasses for then?

A better approach.

@warrenator

 I'm guessing feedback. It's a message board.