Beat the game once to unlock all of the Extras in the menu. This includes Tactician Rating, Sound Test and Movie Gallery.
Train your lords in arenas smart or in combat not very smart to the combined level of 50 before the level "Four Fanged Offense" and then you will access an alternative "Four Fanged Offense" level where you are in Bern and you do not get Wallace. Instead, a level 3 Warrior appears to the bottom right of the screen named Geitz. If you talk to him with Dart then he will become yours.
In Lyn's Quest, train Nils to at least level 10 this can be done by making a character wait every turn and than letting Nils Play for them. After beating Lyn's Quest, begin Eliwood or Hector's Quest. when you get to the level "The Dread Isle", beat it in under 20 turns to be asked to embark on a side quest. Accept this and you will enter the level "Prisoner of Magic". After a few turns in this level a Magic Seal unit called Kishiuna will appear. Kill the boss, than surround Kishiuna. If you kill him, than you will be asked to embark on another side quest called "A Glimpse in Time".
To unlock Hector Mode, beat the game once.
In the Nabata Desert Level Living Legend, Use a thief or Canas and move him to the area near the place where you first see Hawkeye. Move him to about 4 squares left of the bottom right of the screen and you will find an Ocean Seal. This seal can change a pirate Dart to a Berserker. If you train Dart to level 20 and then use the Ocean Seal on him, than he will become significantly more powerful than Hawkeye.
Get Hard Mode
To unlock Hard Mode, beat the game once.
Get Jaffar to Join Your Party
Get Nino to join your party and in the same chapter have Nino talk to Jaffar.
"Valorous Roland" Chapter 28 Tip
Mclose enough to a lava square to make an enemy stop on it to deal damage to him.