The key here is to target the point spread five and seven, because these are virtually tied as the most common margins of victory. It's important to recognize that most betting sites are only willing to sell 2 or 3 half points for 10 cents each, after which point they start charging more. Some sites sell up to four half points at this price though.
The negative (-) sign indicates that the Cowboys are the favorites, while the positive (+) sign indicates that the New York Giants are the underdogs. With the spread set at 2.5 points, a bet on the Cowboys would mean that they would have to win by more than 2.5 points (3 or more) in order for you to win that bet. A bet on New York would mean that the Giants would have to either lose by 2.5 or less points (2 or less) or win the game outright in order for your bet to win.
The point spread is a handicap placed on one team for betting purposes only, it has no place in the game itself. It's designed to give both teams an equal chance at winning in the context of wagers. Think of it this way: If last season's Super Bowl champion was playing a basement-dweller team that hadn't won a game all year, that's a shoo-in bet. Of course, you're going to take the Super Bowl champs, and in all likelihood, you're going to win. What's the fun in that? Even your bragging rights would be next to nil.
That was all before Charles McNeil, a math teacher from Chicago, invented the concept of the point spread. An avid gambler, McNeil created what he called “wholesaling odds” and started his own bookmaking operation in the 1940s. He started out offering this new style of betting on football, but his business model grew to include basketball. McNeil changed the way sports betting was done, and his legacy lives on today in what we now call the point spread.