Over the last 3 nights I've been using a college b ball system that has hit wildly..I'm using stats from scoresandodds.com
Take Home team ppg + Road team points against and divide this by 2 (taking the average of these two numbers)
Then take Road ppg + Home team points allowed and divide by 2. Subtract these two numbers to come up with a new spread.
These have been great in determining ATS bets and I've even drawn a few underdog ML victories with this system.