Start the game in three-season mode and win the Super Bowl three times in a row with the same team. If you can pull this off you'll find new players in the Free Agent section after your third Super Bowl win.
Get Extra Create Player Points
When you are creating a player, before you make him, check to see how many lines of points he has. If you are not satified than leave the player uncompleted. Repeat this two or three times and your player should have at least three full lines of Power.
Special Ending
Beat the Super Bowl 3 times in a row to get the credits and a better ending.