If the public comes out and bets really hard on one side, the line is going to move a lot making the odds worse on that side and a lot better on the other side. If you’re planning to bet against the public, you should wait to bet until the line moves as far as you think it is going to. Be careful, though, if you wait too long and some big money bettors bet, they can move the line back.
Notice that point spreads adjust the score for the favorite team. This is easiest to see with an example: If the New York Knicks are playing the Boston Celtics, and Boston is favored to win by a 4-point spread, then a bet on Boston only pays out if Boston wins by more than 4 points. A bet on New York pays out if New York wins or if they lose by less than 4 points.
Technically, probability should always be a number between 0 and 1. It's often expressed as a percentage though, which makes things easier for the purposes of betting. 0.7059 converted into a percentage (i.e. multiplied by 100) gives us 70.59%. What this means is that the odds suggest the Celtics have a 70.59% chance of winning. If we believe the Celtics have an even greater chance of winning, then we should back them at odds of -240.
Let's use our example from earlier, but this time let's say you think that Florida will cover the -7 spread. Should you place this bet? Maybe. Yes, this is good value bet and one that you should bet, but maybe not right away. Let's say you think the public is improperly going to dump a lot of money onto Arkansas. If this happens and you wait to place your bet, the line might move in your favor. By waiting, you may be able to get Florida at -6.5 to win. This means that if you bet right away, you would only tie if they won by seven points. By waiting, you will win your bet now if Florida wins the game by seven points.
In an effort to have equal money on both sides of a wager, the sportsbook operator will move the point spread to attract money on the side that customers aren’t betting on. The odds for a point spread might change before the actual point spread. There are certain point spread numbers, like 3 and 7 in football, the sportsbook operators would like to avoid moving away from since they final score margin falls on these two numbers most often.