Sneak Attack (Lv. 15) = grants the user a modified critical hit on the next attack if and only if the attack is done against the monster's back (possibly known with a 11.25 degree off-center leeway from the center). Additionally, this attack is a guaranteed hit if the player is facing the target's back. Whether successful or not, the Sneak Attack condition is removed until it is performed again. DEX is widely believed to be a modifier for this skill.

Trick Attack (Lv. 30) = grants the user a modified attack if and only if a party member, engaged or not, is standing directly in front of the player, effectively being between the player and target. The modified damage is less than what Sneak Attack grants but an added effect (and very important) is that the entire hit is treated as if the player, who is standing between the thief and the target, executed the hit and the total enmity will be applied to him/her. Whether successful or not, the Trick Attack condition is removed until performed again. AGL is widely believe to amplify the damage multiplier.

The effects are stackable, meaning that both modified bonuses apply and stack if both conditions are met. If one or the other condition is not met, then only the bonus where the condition is met is applied. That means that if the thief is behind the target and a party member is directly in front of the thief and between the monster, then both bonuses will apply for a hit that deals substantial damage. This technique has been dubbed and commonly referred as fuidama.

(THIEF) --> (ALLY) --> (TARGET) <-- (TANK)

Essentially, the "tank" may not necessarily be the main party tank, but merely the "tank for this instance". The "TANK" is simply the person who attracts attention so the target is facing away from the THIEF and ALLY. When the THIEF executes both Sneak Attack and Trick Attack and lands the hit, the enmity accrued from that hit is applied to ALLY. This is what many refer to as "hate management" since the Thief has effectively placed massive amounts of hate on ALLY. Note that this "straight-line" model should be taken literally. This does NOT work if the formation is not in a straight line. "Behind" means "directly behind", not "off to the side a little or directly to the side" as how some players seem to interpret it.

Prior to the mid-December patch, a variant (and much leniant) version of this existed dubbed yokodama, where the thief can be as wide-ranged as 90 degrees off-center, so the SATA attack can be applied directly from the side if another party member stands between them. However, the patch has reduced the Sneak Attack's attack solution to be a 22.5 wedge of the target's back, effectively eliminating yokodama from existance.

Many factors are applied into the damage. In general the damage applied is simply a model of a function f = (+STR, +DEX, +AGL, +Attack, -MonsterDefense, +WeaponBase), which is why it is very important for thieves to have bonuses of whatever type to maximize damage dealt to the target.

This brings up the obvious question: Can't the thieves do all the work by doing two attacks and leave the party alone? True, there is nothing stopping the thief from doing that, but the damage dealt will be substantially lower. If the party does not line in proper formation then the thief is relegated to doing Sneak Attack and Trick Attack seperately, which will look like this: f1 + f2 = (+STR, +DEX, +Attack, -MonsterDefense, +WeaponBase) + (+STR, +AGL, +Attack, -MonsterDefense, +WeaponBase). If the monster defence is very high, then essentially it is being applied twice in the fuction and will be buffered twice, reducing the damage dealth, thus the sum of both attacks is lower than having done one massive hit (where MonsterDefense is calculated once). Once your projected offensive damage has reached past the monster defense, which is a static threshold, everything after that is pure damage. This is why doing SATA/fuidama is the most effective way to take advantage of a thief.

Weapon Skills

Certain weapon skills such as Wasp Sting and Viper Bite will also stack its bonus with fuidama/SATA, ultimately dealing stratospheric damage if performed correctly (Viper Bite has an effect of dealing double damage and adding poison to the target). Keep this in mind on whether or not to include the Thief in WS chains. Additionally, if the Viper Bite is chained, the following skillchain damage will be proportional to the Viper Bite fuidama damage. An example of this is doing 500 damage with SATA-VB after Samurai starts with their WS, and the following Distortion did an additional 400 damage.

In the case of two thieves

(THIEF-A) --> (TANK-A) --> (TARGET) <-- (TANK-B) <-- (THIEF-B)

This may take a little more effort, but the model is really simple since the both THIEVES are on the outer part with TANKS sandwiched between them with the TARGET in the middle. However, once the party gets this down a couple of times, replicating this is very easy once the timing has been established. Again, the line-up must be perfectly straight or pretty darn close or this will not work or work only partially.

Unlike the first model, the tanks should be less arbitrary. Whereas the TANK in the first model will only have temporary hate/enmity , and ultimately the enmity will be transferred to ALLY and the TANK will lose aggro. With two thieves, the ALLY becomes the new TANK as soon as fuidama is performed, and the other ALLY will become the new TANK when fuidama is performed by the opposing THIEF. Since both TANK/ALLY players will be receiving considerable enmity, it is more desirable that they are properly suited for taking hits in case something screws up and the massive enmity fails to apply to the other ALLY/TANK.

As suggested by Alienone, you can also have the two thieves on one side.

(THIEF-A) --> (THIEF-B) --> (TARGET) <-- (TANK)

Essentially the TANK will draw enough hate within minute intervals so the TARGET will face TANK, meanwhile, both THIEVES switch places and take turns executing Fuidama off each other. This is a preferred way among thieves since it's easier to manage and it also allows Thieves to easier control when you perform fuidama.

Classic Case with a Paladin

Thieves love Paladins, and most parties will include one or the other. However, the tempatation is to let the Paladin get the initial hate and the Thief tricks off the other melee. However, it is highly suggested that you "seal the hate" with the Paladin early on which will minimize the chance of the Paladin losing hate in any point in the fight.

Execution:

1.) Allow the Thief to pull.
2.) Thief runs to target and before using a ranged hit, starts Fuidama.
3.) After using the ranged attack, the Thief runs back to party while the NON-Paladin (or any non-dedicated tank) provokes the TARGET when in range.
4.) This provocation is only temporarly, enough to allow the Paladin and Thief to get in position so that the Thief can use Fuidama behind the Paladin to "seal the hate" BEFORE the Paladin starts provoking or chainspelling.
5.) Since Fuidama was invoked early on, it should only be a few more seconds until you can do it again against the temporary tank, but the Paladin would have accrued so much hate from the start that the monster will not focus on the temporary tank (or at the very least no more than a few seconds in my experience).
6.) Repeat Fuidama against the non-Paladin melee every minute.

Initial:

(THIEF) --> (Paladin) --> (TARGET) <-- (Provoker)

Afterwards:

(Paladin) --> (TARGET) <-- (Provoker) <-- (THIEF)

Hate / Enmity Management

Because of varing parties, I have seperated out two types of tanks by class, which I call a 'weak tank' and a 'strong tank'.

Strong tanks include PLD, WAR, and NIN because they are able to wear the most defensive armor in the game and naturally have the highest Defense stat. Ideally, they should be the ALLY where the enmity from fuidama is applied to them. This effectively 'seals the aggro' on the Paladin / Warrior since their process of provoking and/or casting spells will ensure that they won't lose aggro. Ninjas, specifically with WAR sub and continuous use of Utsusemi is also a strong candidate because the tank never takes damage.

Weak tanks are basically all other classes except WHM, BLM, and SMN. They include: DRG, SAM, RNG, RDM, THF, MNK, BST, DRK. They are not ideal to hold the final enmity dump but can serve as the initial TANK (to draw monster attention away).

Because of this, a good setup is for the Paladin to NOT draw and seal all the hate at the beginning and let the Thief transfer hate to the Paladin before the Paladin starts chain-casting and chain-Provoking. The person who has initial hate can be any of the weak tanks mentioned above by pulling using a ranged attack, Provoke, or casting a spell. The hate will be transferred to the Paladin once the Thief executes fuidama.

(THIEF) --> (PALADIN) --> (TARGET) <-- (RANGER/PULLER)

Note: From my experience, Dragoon also works as a either an ALLY or TANK because they have the armor to do either, but at the same time can lose the hate from using High-Jump if they are the ALLY (final tank), which can be a great asset setup if your party does not have a Paladin. Not 100% sure about this, maybe you Dragoon folks out there can clarify on this but every time I transfer the hate to a Dragoon he/she immediately jumps after that and the monster goes back and wails on the original TANK.

A Thief's Pet Peeve

The following outlines the general things that players should avoid when they have a thief in the party. Doing the following tends to irritate if not annoy the thief very much, and may cause the thief to make demands (which in my opinion are not unreasonable). Everyone in the party loses if they are not letting any member do their potential. Most thieves do not like to do their job half-assed and will be considerably upset if no one cares to position themselves properly. I know that it's probably irritating to have a thief yell for everyone to be in position, but the party at the same time has a responsibility to move in position properly - it is not that hard. And for those who still think that they don't have to, then let me say this: Not cooperating and exploiting the thief's potential damage is like telling a black mage to cast Stone instead of Stone II. Everyone in the party loses if players do not exploit the advantages of their jobs/classes.

The tank moves around for no reason, running in circles, or belives that 'manual dodging' works in futility. Don't do this. Even if manual dodging were real, the benefits and effects of fuidama(VB) should offset this and ultimately the hate will be drawn away from you.

ALLY (which, discussed above, is the final tank) attacks the monster from the side, ignoring Thief's request to stand behind. The majority of offenders do this, and I really don't see why. You do not get some special attack bonus for attacking the monster's side so why do it?

Warriors not in the setup (for whatever reason) provoking haphazardly. This is somewhat of a delicate setup, since this is all part of hate management, there should be no extraneous or unnecessary provoking which may ruin the timing and setup.

Mages/Rangers that forget that their actions accrue a lot of hate in the beginning. Please wait until after the fuidama is performed before casting WorldWarIII or Barrage. Those skills have, in effect, the same as Provoke and since mages and rangers are typically away from melee distance, this causes the entire setup to collapse.

Lastly, and probably the most prominant, Behind means directly behind. Not "a little off to the side", or "somewhat a degree off because I feel like it". It means behind - I don't see why some people like to open this for debate because there is no debate... behind is behind. A good way to check if you're lined properly is if the tank the monster is currently facing is also in the middle of your screen.

If you are a card-carrying member of the National Association of Kleptomaniacs

If a ranger does not exist in your party, a Thief is a perfectly acceptable puller. Since they use boomerangs and have a fairly decent throwing skill, they can also do a little bit of hurt before the fight starts. Additionally, having the highest evasion skill (along with Ninja) never hurts either if a pull goes bad either by getting bogged down while moving to party or if the pull was too close. More than likely, the monster will miss a few times, and all the WHM/RDM needs to do is slap a Regen on you when the fight starts.

If you do go out and pull monsters, use Sneak Attack and Trick Attack before pulling. This will effectively pre-buff you and starts the timer before the fight starts. The one minute should be enough for you to pull, get back to the party, and land your fuidama hit and just in time to start a second fuidama attack. Tweaking around with the timing takes practice, but if the necessary players align themselves fast enough, this can be done reasonably within a minute. The result is that you will be able to land at least two fuidama hits nearly immediately and the party will have a substantial advantage in the fight's early stages.

If the line formation becomes broken and you have already executed Sneak and Trick Attacks, then disengage from the fight. Do not waste the next hit and notify the party that the formation line has been broken. Give the party some time to realign themselves before reengaging. That way, you will save the monster hit instead of throwing it away. If the party yells at you for disengaging, then they clearly don't know about fuidama formation or even worse, don't want to know about formation. Time to find a new party - it does no one any good for thieves do their job half-assed.

Take a minute and discuss the fuidama setup and make sure everyone is on the same page before fighting. Dealing 300-600+ damage in every fight will save a ton of time if you're partying for XP, and everyone wins.

The Paladin and Thief is like bread and butter (Thief and anyone with Provoke too). Whenever possible apply the Trick attack behind the Paladin so the aggro is dumped on the Paladin and no one else.

Lastly, by the time you are at Lv. 30 always, always, always use Mithkabobs. Mithkabobs give thieves STR, AGL and Attack bonuses which is pretty much anything a thief can ask for. Their fuidama deliver monster damage, and there is almost no reason why any thief which can steal or farm for cash, should not be using Mithkabobs.

If you can afford it, it's more optimal to use most of the cooked fish. This is actually better than Meat Mithkabobs / Chiefkabobs. I suggest Roast Pipira, which gives +3 DEX and +14% Attack for 30 mins., which goes a long way to helping general attacks and Sneak attack damage (remember you want to focus on DEX than AGL since Sneak has a higher multipler than Trick). Broiled Pipira lasts for one hour instead of 30 minutes and you don't lose -1 MND (not that it really matters much).

Recommended Foods for Thieves:

Meat Mithkabob: +5 STR, +2 AGI, -1 VIT, -1 INT, +22% Attack for 30 minutes.

Meat Chiefkabob: +5 STR, +2 AGI, -1 VIT, +1 INT, +22% Attack for 1 hour.

Roast Pipira: +3 DEX, -1 MND, +14% Attack for 30 minutes.

Broiled Pipira: +3 DEX, +14% Attack for 1 hour.