When you reach Balamb Garden On Disc 3. The Triple Triad Card Group will start to appear. Challenge them, in a certain order to defeat them, and recieve some better TT Cards. The easiest aspect is to locate the members, the hardest aspect is the win. Please note that to win, you'll need to have a avid knowledge of Triple Triad, and to make sure you understand that it will take a few tries.. and a constant reseting of your Playstation.

Jack : 1st Floor Elevator Lobby. (Directory Board). Tells You about the Card Club.
Club : The Man Walking near the Dormitory, Cafeteria and Parking Lot.
Diamond : Two Girls, They Walk toward the Directory.
Spade : The Boy who gave you the cards in the Begining Of the Game.
Heart : Xu in the bridge of the Garden.
King : Converse with Nida after defeating Xu (Heart), later talk to the Doctor in the infimary (Use Square Button). Turns Out she's the King. Go to Squall's room and choose to be alone, save and sleep until Quistis and the King appears. After this fight, she will play you on the bridge of the Garden.
Joker : Draw Point in the Training Center.

If you have eventually defeated all of the members in Disc 3, they will appear in Disc 4 on the Ragnarok, they also carry some useful cards.