Note: For things such as Golden Apples and Soma Drop, the best method to farm these is via "MuudSuud" in Kefka's Tower. (Path #2, the room right after the toilet area.) He has a 100% Ragnarok morph rate, 25% chance to become a Soma Drop. Bet this at the Coliseum for Golden Apples. As for X-Potions, you can repeat the "Finding Food" quest in WoR Albrook by flying back and forth to grab fish for the bartender.

Also, I'll list only the stuff worth aiming for within reason and not trying to grind say, Hi-Ethers or something at a 4% rate off a level 70+ monster that takes forever. Not to mention a lot of drops can be easily acquired at the Coliseum, so refer to that file for a guide if you're wanting a specific item.

One more thing: If you're trying to cheat the system and get a rare drop, the game determines the drop when you enter the battle, however, if you don't get the item you want, reload and do another fight to change the RNG, then try again. Helps mostly for monster-in-a-box or certain boss fights.