Originally posted by fallen_cloud
You gotta get your chocobo to A class first. Then win 3 races in a row. Then you'll rise to S class.
S stands for something like 'Special', it's a rank greater then A not less.
One Mime is fine, but first time around I beat Emerald Weapon with 2 Mimes. Of course you can only use one against Ruby Weapon anyway, unless you luck out and revive your characters.