Easy Goals
As you get the ball, if your on a breakaway and you get too close to the goalie he will come out of his net and dive on the ball. You can avoid this by running tword the net. As the goalie starts to dive, push C-Up. This will allow you to jump over the goalie and get an easy goal.
Credit Goes To: MjoeT316 via IGN 64

 Easy Goals
 Get Ronaldo
 Play As Atlanta

Get Ronaldo
To get Ronaldo in Fifa 99, go to either Brazil or Inter Milan and you will see a player named G.Silva. Then go to player edit and change his name to L.Ronaldo.
Credit Goes To: Al Morrison via IGN 64

Play As Atlanta Attacks
To get the Atlanta Attacks, win the cup with Brazil in professional mode.
Credit Goes To: Nintendo 64 Freak via IGN 64