Delete your monster:
if you happen to accidentally get a monster you do not want (usually by pressing X too fast when regenerating monsters), you can get rid of it for good. When you go to the association and select "Retire", the lady will ask you if you want to freeze it. Tell her "No". She will then ask if you want to retire it. Tell her "Yes". It will not use up a spot in your freezer and you will get rid of an unwanted monster.
Easy wins:
A very easy way to go through the storyline quickly is to get a monster dedicated to Power and Accuracy, Train it in Power and Accuracy mostly, but have all its other stats at level 10. The power and accuracy easily raise to level 20 to 30. Most monsters through E, D, C, B, and A classes will not be able to dodge your attacks, and they will be KOed in one to two moves. This works well against Bosses and in dungeons, since they attack rarely which leaves them wide open for quick attacks that will do devastating damage. Having 700 Power and Accuracy makes the final Boss very easy to defeat in both forms. Note: Monsters such as Bleakons are perfect for this, since their Power and Accuracy are raised quickly and easily.
Easy training:
If you have a new monster that has trouble in adventures, use this trick to get it leveled up faster. Go to an adventure, it does not matter where. Make sure you have a powerful monster in your party. Battle an enemy, and instead of KOing them with the powerful monster, weaken them so that they only have a sliver of life renamining. Then, switch with your weaker monster and allow it to finish the monster. The experience will be rewarded mostly to the weaker monster. This is an easy way to give it experience and allow it to gain new attacks and abilities.
Get rid of unwanted traits:
When you fill up the traits on your monster's data you can get rid of unwanted traits like Genius. To do so, level up until you get another trait. You will be asked if you want to delete a trait to make room for a new one.
Unlock Secret Monsters
By putting various DVDs, games and/or music CDs into the game, you can create secret monsters. Here are some of the monsters that can be created using this technique:
Baseball Boy: Field of Dreams DVD
ChaosDragon: Crouching Tiger, Hidden Dragon DVD
DuckFever: Cats and Dogs DVD
HipMew: Cowboy Bebop: The Movie DVD
Kagemusha: Onimusha 1 PS2
Kasumi: DOA: Hardcore PS2 game
MahjongKoro: Britney's Dance Beat PS2 game
Metal Jell: T2 Extreme DVD
Miku: Fatal Frame PS2 game
Peacocken: Fischerspooner #1 CD
Pipo Ape: Ape Escape 2 PS2 game
Pirate Ape: Splinter Cell PS2 game
RygaRoller: Rygar: The Legendary Adventure PS2 game
Surfana: Justin Timberlake Justified CD
The Perfect Schedule
I find this the easiest way to train your monsters without them getting tired. I put in various ways for the level of the gadget you decide to use:
LEVEL 2
Week 1: Level 2
Week 2: Level 2
Week 3: Level 1
Week 4: Rest
LEVEL 3
Week 1: Level 3
Week 2: Level 1
Week 3: Level 1
Week 4: Rest
LEVEL 4
Week 1: Level 4
Week 2: Rest
Week 3: Level 4
Week 4: Rest
Here's an example of how to do this, I'll use a Level 3 schedule
Speed Training
Week 1: Pitching Mac
Week 2: High Jump
Week 3: High Jump
Week 4: Rest
This work all the time and if the monster has a tiny slither of fatigue in him just use an Oily Oil on him. You can buy them in Visley.