Have the Game Boy Advance games Madden NFL 2005 or Madden NFL 06 in the cartridge slot. Go to "Madden Cards". The game will detect the Game Boy Advance game, and you can buy a bonus set of Madden Cards.
High stepping into endzone
When you are running very far out in front of everybody and are by the endzone , hold X. Your player will high step all the way into the endzone.
In NFL Superstar, choose your answers to interview questions wisely. The answers will affect your personality type and most endorsement companies want a player with a more conservative personality type, such as "Team Leader" or "Professional".