Preface
In the spirit of the original Maximize DPS 101 thread, one of the single most beautiful contributions to better WoW players on the internet, I will try to gather as much information as possible and display in this thread while doing my best to give recognition to those who did the labor. For the background of the information (including mathematical, parsing, log, and gear analysis), please see the original thread by Graf here.

There is no rotation to Shadow Priest in regards to maximizing DPS. A set rotation is used for trading DPS for convenience, otherwise known as "facerolling" (much better results if you are another class, facerolling as an spriest is not a great idea).

More resources:
"I do ___ DPS"... found in Combat Log parsing here.
Information on gear, Best in Slot lists, and stats can be found at Izolight's BiS Gear List
"Should I gem"... and other gear related personal questions will receive faster response here.

Lingo:
MB - Mind Blast
MS - Mind Sear
VT - Vampiric Touch
VE - Vampiric Embrace
MF - Mind Flay
MF2 - Mind Flay 2 ticks instead of 3 ticks (also known as clipping)
DP - Devouring Plague
SW:P - Shadow Word: Pain
DoT - Damage over Time: VT, DP, SW:P, and Shadowfiend as we don't need it for mana
GCD - Global Cool Down
DPEt - Damage per time to execute
P&S - Pain and Suffering, a talent that refreshes the SW:P timer through Mind Flay impact.
Haste Rating - Haste rating, the number on gear and in the character pane that is not a percentage
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Basic Information
-Get a DoT timer to see the EXACT expiration of your DoT and one that tracks DoT's on multiple targets. If your DoT timer does not include tenths of a second, dump it and get a new one (there is no "best", the "best" is the one that presents the information to result in the highest DoT uptime for YOUR shadow priest).
-Get a cast bar that includes estimated latency within the cast, then learn how to use it. You can combat and win against the lag beast.
-Get a very recognizable cooldown tracker.
-Get a mod to notify you when Inner Fire expires (through charges or time)

Shadow Weaving: Stacks are on you, the player, as a buff; they are not stacks on the target. Thus you can "build up stacks" and switch targets without worry of loosing this buff. Only time and death can remove this buff from you. VE does not create a stack. MF and MS create one stack "per tick" during the channel, instead of per cast. All other shadow damage dealing spells create one stack per the spell landing.

For max damage output, ensure the following buffs are always on you. Other roles will require different flasks and/or food (soakers/ranged tanks for example):
-Flask of the Frost Wyrm
-Fish Feast or Shoveltusk or Firecracker Salmon
-Inner Fire
-Shadowform

Keybinding:
There's hundreds of topics on this, thought I would throw my hat in on the subject as well. Visual queues on the HuD to notify you that certain actions are needed will best be handled through muscle memory reaction instead of cognitive awareness to recognize where a button is, hover, and click. On single target, non-movement fights, keybinding has no advantage over click casting outside of the spell queue. On movement fights or multi-target fights, keybinding will increase your dps over time. *offtopic: Does anyone know of a converted keybinder? (keybinder -> clickcaster).

If you have a set rotation of spells or use a macro to create a set rotation, your dps can be increased by doing it manually. However, your dps can also decrease if you screw it up. If you do use a macro, ensure you learn and understand how and why it works. Every now and again: take a trip to the training dummy and try to 'beat the macro'. You may be surprised...
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Openers
An opener is a sequence of spells to be performed when first engaging a target and is not to be repeated. Do not waste any time, as soon as one cast finishes you should be into the next one for the entire fight.

An opener should accomplish the following:
1. Open with Misery (VT, SW:P, and MF provide Misery)
2. Cast/recast SW:P after acquiring 5 stacks of shadowweaving

If your opener accomplishes the above, it is no worse nor better than someone else's opener.

A few examples, this is not the complete list of options for openers:
VT-DP-MB-MF-SW:P
MF-MB-VT-DP-SW:P
SW:P-MF-MB-VT-DP-SW:P
MF-MF-VT-DP-SW:P
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"The Rotation"
We do not have a rotation, we have a priority list of which action is best to perform before others for highest damage output.

When should I recast SW:P for maximum benefit to buffs/procs?
Details and ongoing discussion can be found at Harb_ID's Shadow Word: Pain and refreshing through P&S.

When should I use SW:D?
SW:D is a very good "movement" spell, use it while running. Use SW:D while moving only and the incoming damage done to yourself is not life-threatening.

When should I clip Mind Flay after the 2nd tick?
For Mind Blast: Don't. Finish the channel and get the 3rd tick then cast MB.
For DoT's: If you are really good at clipping MF at 2 ticks, keep going. If you are not sure, an add-on such as Gnosis or investigating the combat log parses at websites such as WorldofLogs or WowMeterOnline can determine your accuracy.

Do NOT clip DOT's!
VT and DP are the only two to worry about. Here's why clipping is evil:
VT is placed on the target at 1:03, at 1:06 will be it's first tick with the second, thrid, etc. until the 5th and final tick is at 1:18. You should begin casting at 1:16.5 (zero haste) to refresh it, but got trigger happy and cast at 1:16.3. Here's what happens:
1:03 VT lands
1:06 VT ticks 1
1:09 VT ticks 2
1:12 VT ticks 3
1:15 VT ticks 4
1:16.3 VT begins cast
1:17.8 new VT lands
1:18 ..... (nothing happens... where's my tick? IT WAS CLIPPED)
1:20.8 new VT ticks 1
You clipped and 5.8 seconds went by between VT ticks, because you cancelled the fifth and final tick. This is bad. As in not good. This lowers damage output substantially.

DoT's priority: It does not appear that VT and DP "best" one another for damage done in most fights while an Unholy Death Knight's Crypt Fever debuff is active on target. For sanity sake, choose the one comfortable for you to cast first.
-Refresh VT when one Global Cool Down worth of seconds are remaining on it's DoT. DO NOT CLIP, better late than early. The accurate time will depend on your hasted VT cast time, figure this out before the fight while raid-buffed.
-Refresh DP after it expires, not before. DO NOT CLIP, better late than early.

Should I stop casting Mind Blast?
Read PiousFlea's Patch 3.3 Mind Blast, the Definitive Math for more information. There are two additional sources outside of the above equation to determine the spell power needed.
1. Simulationcraft. Run your priest through this simulator. Then re-run your priest through this simulator removing all reference to Shadow Word: Death or Mind Blast from the "actions" list. Be sure to set an appropriate "delay" setting for your raiding conditions as well as ensure that the Buffs and Debuffs under options apply to your situation/raid composition. For example, if you have an average latency in game of 100ms and finish your MF channel to safely recieve the third tick, you could add the following variables:
2. Use the following spreadsheet to find out how much spellpower your priest would need with zero, zip, zilch, nada human error attached to this post.
Beginning testing of the loss/gain can be found here.

What about Replenishment after I have decided to drop Mind Blast?
If your raid needs it, offer it. It can still be a damage output gain to cast MB to refresh Replenishment (15 seconds) loosely within the 15 second window than to have strict cooldown management displacing other spells to cast MB every cooldown.
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The Priority List
1. DoTs (VT and DP)
2. Replenishment
3. Mind Flay

Explanation:
1. DoTs - Vampiric Touch and Devouring Plague take priority over all else. Try to maximize their uptime, your total damage done will increase as a reward.
2. Replenishment - This buff requires refresh once every 15 seconds. If your spell power is greater than the minimum required to drop MB, then MB only needs to be cast enough to keep Replenishment active. If your spell power is less than the minimum required to drop MB, then MB should be cast immediately after finishing the current action when MB's cooldown expires. Finish your MF cast, do not clip. If your spell power is greater than the minimum required to drop MB and you are not needed as a source of Replenishment, then skip this priority and only use 1 and 3.
3. Mind Flay - this should fill ALL dead time. Mind Flay is no longer a filler between MB cooldown expirations, Mind Flay is now THE filler between all casts. If your shadowpriest currently has nothing to do, cast Mind Flay. Do not wait 0.x seconds because another action will be needed in the very short future: Cast Mind Flay, finish, then perform that other action.
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More DPS Needed!
Inner Focus:
The spell is two components in one. The "mana savings" of the spell will work on all spells that cost mana. This consumes the buff and ends it's benefits. The "crit chance" only works on certain spells in our arsenal (in order of maximum crit benefit):
1. Mind Sear - crit chance applies to the entire channel, all 5 ticks.
2. Mind Flay - crit chance applies to the entire channel, all 3 ticks.
3. Mind Blast - crit chance applies to the spell.
4. Shadow Word: Death - crit chance applies to the spell.
5. Improved Devouring Plauge - crit chance applies ONLY to the "Improved" initial damage.

Pre-pot! Pop a potion before entering combat. Ask your RL if you can have your tank count down before the pull (when possible). Pop a Wild Magic Potion when you hear the tank say "2". If you do pre-pot, weave your Shadowfiend into your opener for the 200 spell power bonus as a nice up-front load of damage done and increases the chance of getting an extra fiend into the fight at the end. Think of the fiend as a 4th DoT, not a mana recovery ability.

If you have conflicts between VT and DP needing refreshed/cast at the same time LESS than 16 times per fight, VT is priority over DP. If you have conflicts between VT and DP needing refreshed/cast at the same time MORE than 16 times per fight, DP is priority over VT. The gain is very, very small. If you find yourself in a situation where more than 16 conflicts arise and Crypt Fever is active on target; DP-VT will net more damage output.

Bloodlust/Heroism, what to do?
Refresh those dots ON TIME and Mind Flay until your eyes bleed. During bloodlust/heroism, it is more pseudo-power to NOT take a potion. Instead, pop a Potion of Speed during a period of the fight where lustism is not going to occur. Some fights require lustism to get passed a very difficult part, if this is the case, it would be less beneficial to you over the course of the whole fight, but more beneficial to the raid if you popped a Wild Magic potion during lustism.

4+ mobs begins the sweet spot where Mind Sear out does multi-dotting for maximum DPS. Mind Sear scales very well with gear, its use will only increase with better gear. Lower health mobs should just be MS'd down. Higher health mobs can see an even bigger increase to damage done if VT DoT's are spread around on the targets while Mind Searing.

For 2-3 mobs:
Multi-DOT!!! This can also decrease your DPS. The time to live on the secondary targets, the GCD's used to damage the secondary targets, and the ability (skill, latency, positioning, strategy employed by your raid, etc.) need to be examined as to whether or not multi-dotting will increase or decrease your dps.

****Note about Pain and Suffering****
Take note that the refresh of SW:P through Pain and Suffering does not take place until Mind Flay lands, it does not perform the reset upon cast. This means that "misses" will not refresh SW:P and the SW:P refresh is subject to server lag, this is different from "latency" that is reported to you through the UI which is network lag. Give a little more time to overcome the lag between you beginning the cast of MF and the target being recognized by the server as afflicted with MF which fires the reset of the SW:P timer.

Aids to Multi-Dotting:
Set a focus and use a modifier to cast on focus target.
Dot Timers that track multiple targets are a great aid.
Keybinding your Multi-Dot spells near one another with modifier's to cast on focus can help.
Remember that depressing both left and right mouse buttons allows you to move forward, freeing your "keyboard" hand for casting.
Keybinding, in general, over mouse clicking can be a great help.

Dangers in Multi-Dotting (things to avoid):
1. DoT fall offs. If the gap between expire and refresh is constantly widening or exists across multiple targets, DPS can decrease below that of single target.
2. Positioning: Chasing the center between targets can get you killed. Careful...
3. Forgetting other priorities: Shadowfiend should be used nearly every cooldown as a damage output, this can be lost in the multi-tasking fiasco of multi-dotting. Don't stand in fire, don't forget your potion, trinkets, etc...
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Raiding Information
Is your inner fire on you? Food buff? Flask? Are you in Shadowform?

Learn the fight: learn it's phases, stages, and length to:
OPTIMIZE your Shadowfiend depending on this information. Do not wait for Bloodlust/Heroism. Do not wait to be out of mana. Send the fiend out as many times as possible in the fight without sending it into impending death. A 4+ minute fight should have 30+ swings from your Shadowfiend. A 6+ minute fight should have 40+ swings... etc. View the Shadowfiend as a 4th DoT, a damage producing ability, not a mana regen.
OPTIMIZE your Dispersion. Is there a time where dps can't occur due to movement, phase changes, talking about how this raid boss will destroy you unlike the other 10,000 raid bosses we've encountered? DISPERSE THEN if you have mana issues. If you don't have mana issues, save Dispersion for an "oh shit" button.

Don't forget about "pre Fade". Learn your tanks. Learn if they need a small amount of time before they peak at maximum generating threat per second. Pre-fading and casting "all out" will result in a higher DPS than the antiquated "pause" or "3 second rule" between the tank's engagement and your own.

Heavy movement fights: The "priority" system should change... your "instant casts" such as SW:D, DP, and Shadowfiend should be organized in a way to maximize their need for casting during running, allowing "stand still time" to be dedicated to MB and MF without loosing DoT uptime. If run-time becomes extended beyond these spells, spamming DP casts for IDP damage can fill in.

Check Your Raid Composition
You should aim to complete this while haphazardly vomitting invites to the unkown:

***Buffs on Player***
30% Inc. Cast Speed
Bloodlust/Heroism - Shaman (all)

3% Inc. Damage
Sanctified Retribution - Retadin
Ferocious Inspiration - BM Hunter
Arcane Empowerment - Arcane Mage

3% Inc. Haste
Improved Moonkin - Boomkin
Swift Retribution - Retadin

5% Inc. Crit
Elemental Oath - Ele Shaman
Moonkin Aura - Boomkin

5% Inc. Haste
Wrath of Air Totem - Shaman (all)

Inc. Spell Power
280 - Totem of Wrath - Ele Shaman
10% - Demonic Pact - Demo Warlock
144 - Flametongue Totem - Shaman (all)

***Debuffs on Target***
3% Inc. Crit
Heart of the Crusador - Retadin (some Prot Pally)
Totem of Wrath - Ele Shaman
Master Poisoner - Assassin Rogue

5% Inc. Crit
Improved Scorch - Fire Mage
Improved Shadowbolt - Aff Lock (Destruction tree)
Winter's Chill - Frost Mage

13% Inc. Damage
Curse of Elements - Warlock (all)
Earth and Moon - Boomkin
Ebon Plaguebringer - Unholy DK

3% Inc. Hit
Misery - Spriest
Improved Faerie Fire - Moonkin

30% Inc. Devouring Plague Damage
Crypt Fever - Unholy DK

Hey, is Inner Fire, Flask of the Frostworm, and a food buff on you?

Sticky!!!

gj

This is an awesome guide. I just got my SP to 80 and was not expecting to find a guide with this level of detail so quickly. Back when I was starting to raid with my shammy, it took me a lot of digging and sorting through dozens of pages (on other sites) to find the info to just get going, and then I had to work out the nuances on my own.

Thanks for the clear and detailed info.

epic.

i hit 80 less than 24 hours ago and pulled 3.1k on emalon and 3.5 on archavon (did tier 6/bear runs at 70 and treated this forum as gospel, so, I'm not retarded.)

i was impressed. but i knew i could do better.

this definitely shows me things i can do better.

Is your inner fire on you?

Took all the great things i knew about shadow and beat it into my head....best post ever!

I see you are using SW:D in your opener/"rotation". My personal advice is only to use it when running, otherwise I find myself loosing 200-300 DPS. Any other thought about this?

SW:D > MF1.
MF2 > SW:D.

Filling a dead GCD with SW:D is optimal if you can't fill it with a 2-tick Mind Flay (or DoT refresh). This doesn't mean use SW:D everytime the cooldown is up. You have to be more picky on when you cast it.

Thank you Rossoneri and Meltface. I have added/reworded the following. Is this an improvement?

Is your Inner Fire on you?

Maybe even more important, Are you in Shadowform?

I ding'd my priest 80 first of this year, and have been healing holy/disc since then. Just made the swap to shadow, and am fairly clueless, so this is some great info.

the only question i have is, how does mind sear work into max dps?

my thought was that in a multi-mob situation, even if you aren't tab-dotting, mind sear would be higher damage than mind flay?

I used to only Mind Sear on mobs 4+, but have gotten lazy and do it on mobs of 3 also. As soon as I see that 3rd one die, I immediately MB/SW:D (depending on health). I'm sure it's possible to do more DPS on a mob of 3 by multi-dotting, but like I said, I just Mind Sear and pull like 3.5-4k DPS on them pretty consistently.

Not at all. This post refres to those situations where you really, really want to push the utmost DPS from your spec and gear - in other words, raid boss fights. If you can manage those, it is assumed you can manage trash easily enough as well.

Well, that's only half of the truth of course.

1. In a Boss fight, with little to no adds, you do single target DPS, and don't use MS at all.

2. In a boss fight with many adds, there may occasionally be situations when it make sense to use MS. To my knowledge, the only boss fights that make sense to use MS in are Kologarn (on the adds that spawn after destroying an arm) and Freya (the big group of mini-adds). And maybe Yogg phase 3, depending on your tactics. (Ok, Thorim arena fight as well, but that's not a max dps situation, the main point is staying alive and keep adds under control)

3. In trash fights, don't bother whether you're doing max dps. If you stay alive and still manage some reasonable dps, that's fine. We're not supposed to out-DPS other classes on short-lived mobs anyway. (That's not to say you can't, just that you'd be taking risks when it's really not worth it )

very nice guide, i have taken note of a few issues i had. Once the server comes back up i will rework my rotation cheers for that guys.

Added comments on Mind Sear based on above.

Fixed error in figuring out possible MB casts.