Eliminate Casting Time:
Right after casting a spell, go to the menu inventory screen. When you return to the game, the spell will instantly take effect. Use this trick if you need to get off a spell immediately.
Dungeons & Dragons Spoof:
At the main menu choose to view the credits and then press X. You will be taken to a hilarious animated skit of a few of the characters from Summoner playing Dungeons and Dragons.
Easy EXP and Bacite Tails:
Make sure your party is at level 13 or 14 and go to Ikeamos Swamp. Make sure you have completed the ring of light quest. Fight the Bacites until you have had enough and leave. If you kill all of them, leave and come back in. They will have regenerated.
If you pause the game and enter the inventory screen and use a magical tract (e.g lightning tract) on a monster and leave the game paused the tract doesn't get used, so you can go back to the inventory screen and re-use it.
Thanks to Revolution readers crooked, Thomas Schofield and Mack Gross!