Steal Tips

The Basics:
Obviously you are going to need a leveled up thief that has most or all the abilities to steal equipment. And naturally, you can't use the steal abilities unless "steal" is your secondary skill set or the obvious: your thief is in the "thief" job class. You cannot steal from ko'd enemies.

Steal Success Rates:
The likelihood that you will successfully steal is based off of the following math formulas, and what isn't mentioned below is that the steal rate is also based off of the zodiac compatibility between the target and the thief. The below math formulas are set that both the target and thief have neutral zodiac attributes. The base number (highest number) for the steal rates are:

-Gil Taking: 100%
-Steal Heart: 50 + MA
-Steal Helmet: 40 + Speed
-Steal Armor: 35 + Speed
-Steal Shield: 35 + Speed
-Steal Weapon: 30 + Speed
-Steal Accessory: 40 + Speed
-Steal EXP: 70 + Speed

-Gil Taking is unaffected by Zodiac attributes.
-Steal Heart dismisses/ignores any evasion rates of the target, but is affected by Zodiac attributes.
-All other steal commands: The base number is multiplied by the success percent of a normal attack.
   -For example: If the base number is 80(%) and the attack percent is 75(%), then the actual/total steak success rate would be 60(%).

Stealing Tips:
Use women most of the time. Most enemies in the stealing chart are male so using women negates the possibility of worst compatabilities which translate into 20% or lower success rates. Also, women can equip Chantages, which insures you're not constantly having to revive them.
Steal from behind because the target's evasion is lowest there. Or set Concentrate as your support ability so it doesn't matter which angle you try from.
Raise your stealer's Speed once you have the battle under control. Yell works the most reliably. Speed Save is alright though is way better if the stealer has a Chantage equipped. Cheer Song is alright but isn't reliable.
If the enemy is a Frog, Chicken, or Sleeping, there will be a bonus to the success percentage. If the enemy has more than one of these statuses, the bonus will be larger (I've seen 70% on Steal Weapon and my stealer's Speed was only 12 with good Zodiac compatability. Normally would be about 52% with Concentrate.) Also, if you try to steal from an enemy who is Charging something, there will be a bonus to the success percentage.
Don't Act, Stop, Confusion, or Sleep disable an enemy's evade percentages. Evade also is zero when Sleeping, Dancing, or Performing.
If you're not using Concentrate and you're not after the enemy's shield, break it. This applys to the weapon as well if the enemy has Weapon Guard or a mantle although in the mantle's case you'd need to steal it.

Story Battle Steals:
Dorter Trade City: Long Bow and Buckler from two different Archers, Linen Robe on Knight
Sand Rat Cellar: Silk Robe on Knight
Thieve's Fort: Spike Shoes on Thief, Bronze Shield and Chain Mail on Miluda, Mage Masher on Thief, Silk Robe on Priest, Power Wrist on Miluda
Lenalia Plateau: Barbuta on Miluda
Windmill Shed: Barbuta and Round Shield on Weigraf
Fort Zekaden: Barbuta, Round Shield, and Power Wrist on Algus
Zirekile Falls: Wizard Robe on Knight, anything powerful equipped on Gafgarion
Zeland Fort City: Wizard Robe on Wizard or Knight, Cross Bow on Archer
Baraius Valley: Poison Bow on Archer
Golgarand Execution Site: Blood Sword on Gafgarion
Lionel Castle Gate: Ancient Sword on Gafgarion
Goland Coal City: 3 Judo Outfits, 2 Mythril Guns, Main Gauche, Orichiculm, and Germinas Boots
Lesalia Imperial Capitol: White Robe on Zalmo
Underground Book Storage Second Floor: 2 Partisans, 2 Platina Helmets, 2 Diamond Shields on Lancers
Underground Book Storage Third Floor: Izlude has 'maintainence' so you can't steal anything from him
Underground Book Storage First Floor: Crystal Helmet on Weigraf
Riovanes Castle Gate: Crystal Helmets on Knights, Platina Shield on Knight, Earth Clothes on Archer
Dogoula Pass: Crystal Helmet on Knight, 2 Oberisks on Lancers
Bervania Free City: Defender and Chantage on Meliadoul
Zeltenia Church: Crystal Helmet on Knight
Bed Desert: Blaze Gun, Flash Hat, and Light Robe on Balk, Crystal Helmet on Knight
Bethla Garrison North Wall: 2 Oberisks on Lancers, 1-2 Crystal Helmets on Lancers
Bethla Garrison South Wall: Air Knife on Thief, Crystal Helmet on Knights
Bethla Garrison Sluice: Ultimus Bow on Archer
Germinas Peak: Ultimus Bow on Archer
Posekas Lake: 2 Ultimus Bows on Archers
Inside Limberry Castle: Masamune, Genji Shield, Genji Helmet, Genji Armor, and Genji Gauntlet
Igros Castle: Defender on Dycedarg
Outside of Morund Chapel: Dragon Rod on Summoner
Chapel in Morund: Dragon Rod on Kletian
Colliery Underground, Second Floor: Blaze Gun on Chemist
Underground Book Storage, Fourth Floor: Yoichi Bow on Archer
Underground Book Storage, Fifth Floor: Save the Queen on Rofel
Morund Death City: Mace of Zeus on Kletion
Death City Presincts: Glacier Gun on Chemist, Blast Gun on Balk

The only other place of significance that has not been mentioned on here is the cool items you can find/steal in the Deep Dungeon:
-Click here to go to the Deep Dungeon guide