Hint: Special Intel
After you have finished the Field Training missions (and in the course opened up the War Room, Campaign, Design Maps and Stats features), go back into Field Training. A very short tutorial called Special Intel is now available that gives you extra gameplay tips.

Hint: Clear Data
To erase all saved game data the easy way, turn on your Game Boy Advance and press and hold right, L and Select at the same time. Be careful that you don't accidentally delete your data, though.
Hint: Soft Reset
Press START + SELECT + B + A
Hint: Ghost Mode
Hold B during turn.