Auto-training
After selecting the type of training, press quickly X. The monster will do the training by himself, and he will win if he's healthy.
Jokers
Train in Goat for awhile to get an item that will let you unlock Jokers from CD/DVD.
Hidden Monsters
Disc - Type - Monster
Lunar: The Complete Silver Story (Disc 1) - Game - Desert Hengar
Lunar: The Complete Silver Story (Disc 2) - Game - Legendary monster
Monster Rancher 3 - Game - Moochi
Spyro: Year Of The Dragon - Game - Ice Gitan
Ace Combat 4 - Game - Desert Karakarakkung
Armored Core 2 - Game - Robot
Suikoden 2 - Game - Forest Raiden
Tekken Tag Tournament - Game - Wrestling Moochi
Fantasia 2000 - DVD - Joker
Magnolia - DVD - Frog
Men Of Honor - DVD - Merman
Bob Dylan: Greatest Hits Music - CD - Marin
Dave Grusin Music - CD - Koronit
Chrono Cross (Disc 1 or 2) - Game - Strange Fenril
Digimon World - Game - Forest Hare
Final Fantasy Games - Game - Fairies
Front Mission 3 - Game - Sea Octipee
Train: Drops Of Jupiter Music - CD - Robot train
Gungriffon blaze - Game - Moochi
Heart Crystal
When a monster dies he leves behind a heart crystal. feed this crystal to another monster to boost his skills.
Skip animations
After selecting the type of training (for example, trampoline in Morx Forest), rapidly press X to skip the animations for the drill. It does nothing to the success or failure of the monster.