Health:

• Heroic:  55M
• Normal:  11M

Keepers:

• Each keeper we ask for help will give us buffs for this fight.   The hard mode is not asking for em.
• Freya - Resiliance of Nature:  Increases all damage done by 10% and healing received from all sources by 20%.
• Freya - Sanity Well:  Standing in the well brings you back to your senses, regenerating 20% Sanity every 2 sec. Damage done is reduced by 50% while you remain in the well. Instant  Two of these green beams will be up the entire fight at the sides of the room.
• Mimiron - Speed of Invention:  Increases all damage done by 10% and movement speed by 20%.
• Mimiron - Destabilization Matrix:  Channels a beam of titan energy that destabalizes the molecular structure of certain Saronite based creatures, reducing attack speed by 100% and casting speed by 300%. Cast on all mobs in the encounter.
• Hodir - Fortitude of Frost:  Increases damage done by 10% and reduces damage taken from all sources by 20%.
• Hodir - Hodir's Protective Gaze:  Allows Hodir to save a friendly target who sustains fatal damage by encasing them in a nearly impenetrable block of ice for 10 seconds. Hodir must rest after performing this action.
• Thorim - Fury of the Storm:  Increases all damage done by 10% and total health by 20%.
• Thorim - Titanic Storm:  Channels a storm of titan energy that periodically strikes at enemy targets with bolts of lightning strong enough to destroy weakened immortal creatures. Without Thorim the Immortal Guardians in phase 3 are unkillable.

The Fight:

First thing to mention is this:

Sanity:  Indicates your overall level of Sanity. If Sanity reaches zero your mind will be permanently under the control of Yogg-Saron. 20 yd range, Instant

Insane:  Yogg-Saron takes control of the target's mind. Damage is increased by 100% and health is increased by 300% for 1 min. The target dies horribly when this effect is removed.

We start at 100%.  Various attacks will reduce this.   When you hit zero, you are perma-MC'd and will see the raid as Faceless Ones.    You will die on your own in a min, or be killed by the raid.   You cannot be battle rez'd.   Well, you can, but your sanity will still remain zero so you'd just get MC'd again.     So losing it is basically perma-death for you.

Freya's beams can help restore it when not on Hard Mode.  Anyways, on to the phases.

Phase 1:  Sara

We're dealing with Sara and adds.   Sara herself is unkillable, by us directly.  A gimmick is employed though.

Sara:

• Sara's Fervor:  Increases a friendly target's damage by 20%, but also increases damage taken by the target by 100%. Lasts 15 sec
• Sara's Blessing:  Heals a friendly target for 27000 to 33000, but causes 60000 Shadow damage over 20 sec
• Sara's Anger:  Inflicts 12500 Shadow damage every 3 sec, but increases Physical damage done by 12000. Lasts 12 sec

As you can see, she still does buff targets during this phase, but basically each of her buffs also fuck with them.   Do more damage, take more damage.   Heal you, then fuck you over with a dot.    Give you a dot, but let you do more damage.

Anyways, there are adds that spawn.   They come at a relatively slow pace, which increases over time.  There's also a gas cloud to avoid, being in them will spawn more adds.

Guardian of Yogg-Saron:

• Shadow Nova:  Inflicts 25,000 shadow damage to any targets nearby when the Guardian of Yogg-Saron dies (including Sara).
• Dark Volley:  Inflicts 8500 to 11000 shadow damage to the entire raid. Reduces healing effects by 25%. Lasts 10 seconds. (interruptable)
• Dominate Mind:  Dominates the mind of the target, temporarily placing them under Yogg-Saron's control. Also reduces Sanity by 4%

As you can see, the way to deal with Phase 1 is to have Guardians die near Sara.   We need total of 8 to kill her off, to end phase 1.   Goal is to kite Guardians away from clouds, though we can use them to quicken the spawn pace.    And to kill them near Sara only.

Phase 2:  Brain of Yogg-Saron

This is where we force Yogg-Saron to appear and similar to C'Thun, we can't really hurt him, and have to deal with tentacles.    Finish off any Guardians.  Meanwhile:

• Dominate Mind:  Dominates the mind of the target, temporarily placing them under Yogg-Saron's control. Also reduces Sanity by 4%. 50000 yd range, Instant
• Psychosis:  Inflicts 7500 Shadow damage. Also reduces Sanity by 9%.
• Brain Link:  Links the brains of two enemy targets. Afflicted targets suffer 3000 Shadow damage and lose 2% Sanity every 1 sec. whenever they are more than 20 yards apart. 50000 yd range, 1.5 sec cast
• Malady of the Mind:  Inflicts 5000 Shadow damage and causes the enemy target to run in horror for 4 sec, then attempts to jump to another enemy within 10 yds. Also reduces Sanity by 3%. 1.5 sec cast
  
• Death Ray:  Blasts the target with a stream of deadly energy, dealing 20000 Nature damage every 0 sec (Instant death).

So this phase is Tentacle phase.   While dealing with them the few things of Yogg's to be aware of.   Brain Link'd people must get close to each other, think of Mother Shahraz, now do the opposite!    Also, it seems you must spread out or risk chaining a fear.    Lasers to avoid.  

Anyways, the Tentacles:

Crusher Tentacle:  Melees hard, has a ton of HP and has an aura that reduces damage done by the raid by 20%, stacks with other crusher tentacles so these must go down fast. Melee-ing these will interrupt their aura but they gain a temporary buff that increases their damage and attack speed when they are hit so this is dangerous if they are being DPS'd.

Corruptor Tentacle:  Casts various debuffs.  Dispellers will need to be on the ball. These are interruptable.

• Curse of Doom:  Dooms the target, inflicting 20000 Shadow damage after 12 sec. Curse dispellable.
• Apathy:  Reduces the attack and casting speeds of an enemy target by 60% and slows its movement by 60%. Lasts 20 sec. Magic dispellable.
• Black Plague:  Infects an enemy target with the plague, causing it to periodically retch uncontrollably and be stunned for 2 seconds. Lasts 24 seconds. Disease dispellable.
• Draining Poison:  3500 Nature damage inflicted every 3 sec. 1400 Mana drained every 3 sec. Lasts 18 seconds. Poison dispellable.

Constrictor Tentacle:  These have very little HP and appear underneath random players, grab them and hoist them into the air doing damage every few seconds until killed.    You are still able to attack / cast heals while in it.

Every 90 seconds or so Portals will open into Yogg-Saron's mind. This also starts a timer.

Induce Madness:  Drives all nearby targets insane, reducing Sanity by 100%. 60 sec cast

The melee dps must take the portals and complete their task (or just get out) within 60 seconds or they'll become Insane.    Also, don't go if your sanity is low, else you won't last long in there without going insane.

There will be a random 3 illusion rooms with tentacles and skulls around.    The skulls cast:

Lunatic Gaze:  Looking into the maw of madness unhinges your mind, inflicting 5700 to 6300 Shadow damage and reducing Sanity by 4% every 1 sec. for as long as you are facing the caster. Instant

So do not face them, it'll be a purple beam at you if you are.   Must move and strafe around with backs to the skull at all times, while killing tentacles.   Kill them all and the illusion is shattered.    Run into the brain room and attack it as much as possible before the 60 seconds is over.   Else you'd go insane.  

Illusions:

• Wyrmrest Temple - You'll be at the bottom of it, the room with the Chamber of Aspects.   In front, you'll see the story of the Demon Soul's creation.   You'll see various colored dragons around the perimeter of the room, those are attackable and your targets.   They'll turn into tentacles upon attack.   There are also skulls near by so you must strafe around avoiding facing em.
• Arthas - You'll see him torturing a prisoner, a champion supposedly.  Anyways, this one the skulls are mostly center room, with occasional ones behind pillars.   Your targets are the worshippers I believe, they are in several packs of 3.
• Stormwind - The Stormind King's assination is going to take place.    Your targets are the Suits of Armor around the room.   Their backs are right agains the walls, and the Skulls are kinda in the alcoves.

And that's the "stomach" version of Yogg-Saron.   Getting Yogg-Saron ('s brain) to 30% ends phase 2.

Phase 3:  Body of Yogg-Saron

Health:

• Heroic:  16M
• Normal:  3M
• Enrage:  5 mins

This becomes a straight dps burn down.    But also dealing with Sara's abilities, and he has Lunatic Gaze (4 sec duration every so often) so don't face him during that.

Faceless Immortal Guardians will start spawning, tank those.  So long as we can have enough dps to beat the enrage timer, and have Thorim helping, we can dps down the Guardians and Thorim will kill them.   Otherwise it's a race to kill him before they kill us.   They also do a Drain Life that can be interrupted.

Another thing of note is that Yogg-Saron can cast Empowering Shadows now to heal the Guardians.   It's a slow cast, so can weaken the guardians quickly to be killed off by Thorim before it goes off.

Heroism go!

Hard Mode:

So each of the keepers give the raid buffs, and using 1 or less is Hard Mode.   Thorim would be the one to use to allow the Guardians in the last phase to be killed.  

This means, without Hodir, raid takes 20% more damage, and you don't get ice blocks to save your raid from potential deaths.   Play with caution to try to mitigate whatever you can.

Without Mimiron, raid will move 20% slower, things attack 100% faster, and cast 300% faster.   This means, running around Brain room is slower, must be done fast and efficiently.    Tanks will take more damage.    Casts will be harder to interrupt, the shadow volley is 1.5s vs 4.5s, and the Corruptors are 2s instead of 6s casts.

Without Freya, well this is the slightly harder part.    Psychosis will randomly pepper the raid with 9% sanity loss.   Guess that's just RNG.   Brain Links are another cause, raid should almost always group up so you're not linked across the room to rape your sanity.   But still spread a little bit to not chain Malady of the Mind around other people.  The Brain room crew, have to be doubly aware of where the Lunatic Skulls are.   Yes, they will start nuking you even before they're drawn in, will have to rely on memory to turn ASAP as soon as you see which room you're in.

Otherwise, the fight is exactly the same, well we also all do 30% less damage than normal, so pick it up.

In the final phase, stare at the Lunatic Gaze timer.    There's a CD on it, so switch back and forth between guardians and Yogg, pretty much every 6 seconds.     You don't want to lose what little sanity you probably have left.   Take it nice and slow and do a lot of turning while getting what dps you can on Yogg.

This fight is quite execution based, and you don't even have to be perfect to do it.   Just stick it through, and calmly burn everything down.

Achievements:

Kiss and Make Up - /Kiss Sara in Ulduar while she is angry with you on Normal/Heroic Difficulty.

This is just kissing Sara when Phase 2 starts.   Macro it.

Drive Me Crazy:  Defeat Yogg-Saron without any raid member going insane on Normal/Heroic Difficulty.

Raid check.  Use the Sanity Wells.   In a good kill, you should get this one easily.

He's Not Getting Any Older - Defeat Yogg-Saron within 7 minutes on Normal/Heroic Difficulty.

 Time/dps check.   Possibly drop a healer, or dps just not take as much damage thing.

They're Coming Out of the Walls - Defeat 9 Guardians of Yogg-Saron within 12 seconds on Normal/Heroic Difficulty.

This sounds like it doesn't need a kill, just a fluff achievement.   So take an attempt, gather 12, aoe them down.   Wipe (probably), then kill Yogg.

In His House He Waits Dreaming - Experience all 3 visions of Yogg-Saron's mind on Normal/Heroic Difficulty

Last I did this, it was bugged, but in a good way, did not need King Llane's vision, got the thing just seeing the other 2.   But this is progressive so don't need all 3 in one kill shot.   Get in and you'll randomly see em all eventually.

Three Lights in the Darkness - Defeat Yogg-Saron with the assistance of three or fewer Keepers on Normal/Heroic Difficulty.

Two Lights in the Darkness - Defeat Yogg-Saron with the assistance of two or fewer Keepers on Normal/Heroic Difficulty.

One Light in the Darkness - Defeat Yogg-Saron with the assistance of one or fewer Keepers on Normal/Heroic Difficulty.

This is Hard Mode.

Alone in the Darkness - Defeat Yogg-Saron without the assistance of any Keepers on Normal/Heroic Difficulty

This is the mode that drops the Mimiron head mount.

Sources:

• http://www.mmo-champion.com/index.php?page=851
• http://www.wowwiki.com/Yogg-Saron_(tactics)