Description :

Sports agents must be certified by the league in which they plan to represent players. For example, a sports agent who wishes to represent NFL players must be certified by the NFL Players Association. Sports certification with a specific league must be maintained; otherwise, it will lapse, and an agent will not be able to represent his or her player during contract negotiations. In addition to gaining certification through a league, sports agents must also be registered with the state in which they reside.

It is also helpful (required for certain leagues) to have a post-graduate degree, which most agents choose to have a law or sport management degree of some sort. Florida State University has a great program in Sport Management, with great alumni.

For more info look into the specific leagues or types of athletes you would like to represent as it is different for each.