Edge

Getting an advantage through massive research or possessing knowledge that is not known by the general public.

Having an edge in sports betting involves finding bets that are more likely than the odds. Since this is the most effective way to become a successful sports bettor, getting an edge is not easy. Bookmakers set odds using data that is often superior to anything a person can prepare. If one manages to find the edge of one side or the other, the next part of the job is to find the highest odds among the available bookmakers.

If you want to succeed, this takes time and may not be possible if you don't have the right tools. You can find margins in different ways, whether it's injuries that are reported before a sportsbook has time to update its odds, or weather changes. Or you can find something in a coach's press conference about how a certain player will get more or less playing time. 
Unless you're a mathematician, these simple things will give you an edge when it comes to betting. Of course, finding news before sports betting can get to it is rare. Before the advent of the Internet, it was easy to find local news before sports betting, but that's no longer the case.

There are other methods of finding an edge, especially if you have a system that ranks a particular set of teams more accurately. For example, you can create your own system for determining your betting line (power ranking), which is better than the one that sports betting provides. Again, this is a time-consuming operation.

Finding an edge in sports betting is not easy, so becoming a professional bettor is easier said than done. While it is possible to find an edge, it doesn't happen every day.