Acquire free Berserk status in any battle.

Step 1: Un-equip all beserk status preventing items such as the Ribbon helmet from the party members you want beserked.

Step 2: Equip the Avenger sword on Kain (or Cecil).

Step 3: Enter a battle.

Step 4: For the Character you want beserked, watch his ATB. You need it to fill up just as Kain attacks. Once this happens, Kains berserk status will be copied to this character and he or she will now be berserked. (You can get your whole party berserked this way)

Step 5: Win the battle. Un-Equip Kains Avenger sword and equip on Kain any weapon you want. From now on until you restart the game, anytime Kains ATB fills up along side any of your other characters, they will be put in Beserk status, unless they are wearing a Ribbon.

Easy rare encounters with one 'Siren'

If you use the Siren item, the game automatically sends you into the rarest encounter on the current floor/part of the world you are on. With just one Siren and the handy soft reset, you can use that one Siren to get a rare fight when you need it, if a save point is nearby.

Simply save the game, then use the Siren and you will get the rare encounter. Do a soft reset (A+B+Select+Start) and the first fight you get into should be the rare encounter for that floor and you still have the Siren item.

A test example that works great is to go to the Summoned Monsters town, then save. Go back to 3F of the Cave of Summons then use the Siren. You should confront two rairyuu/Thunder Dragons. Do a soft reset, then go back to 3F and walk around until you get into a fight. It should be with two Thunder Dragons. Use this to get some of the harder to encounter enemies if you do not have a large stock of the Siren item.

Equip Adult Rydia with White Mage staffs.

When Rydia returns as an adult she no longer has the ability to use white magic, so she can no longer use staffs (but still can use rods don't confuse the two) First off you must beat the game with her in your party and go to the lunar ruins and start her trial. When she is young again she has white magic again so you can equip her with staffs. Finish the trial with a staff equipped and even when she returns to an adult she will still have it on. But if you unequip it she will not be able to equip it unless you return to her trial in the lunar ruins. And now your black mage summoner has a white mage weapon.

Fight Flan Princess without using Siren/Alarm

The Flan Princess can be found in the final Lunar Subterane area on Floor B5 in the southeastern most room. This enemy has the probability of dropping a Pink Tail which can be traded for an Adamant Armor, the strongest armor in the game. The rate at which you fight the enemy and the rate in which it drops the item however is very rare (1/64 chance for both). Follow this process to be able to fight a set of Flan Princesses very frequently without having to use a Siren/Alarm item, and in turn greatly increase your chances to score a Pink Tail:

1) Get to the room on Floor B5 where you can encounter the Flan Princess. It is a room with a treasure box in it, and the room is shaped slightly like an unspide-down L.

2) Quick save the game when you enter the room, and once you come to the Final Fantasy 4 title screen, cut the power off to your GBA system.

3) Turn your game back on, go to the main menu on the title screen, and select Continue. When given the option to continue your quick save, press B to go back to the title screen.

4) Select continue again from the title screen, and this time, select Yes when given the choice to restart your game.

5) Walk around within the room. One of two things will commonly happen. You will either immediately fight a group of 5 Flan Princesses within taking a few steps.

or

You will fight a series of 5 battles. The first battle will be a Gold Dragon and a Silver Dragon, and the next three battles will be Dinozombies respectively. Run from these battles if possible. On your fifth battle, you will fight a set of Flan Princesses.

For each battle you complete, you will score a large amount of gold and a decent amount of experience. You will also have a chance for an item drop. As soon as you finish a battle, quicksave, and restart the process as many times as you wish to fight as many Pink Princesses as you can.