HIT Rating

This is the most important/valuable stat for an enhancement and elemental shaman.
If you want to start raiding you must have reached hit cap.
Elitist Jerks article on enhancement shamans says:

Changes to the unified hit rating mechanic and an increased use of spell damage abilities due to Maelstrom Weapon have greatly increased the need for Hit Rating for Enhancement Shaman. While there is still no need to reach the DW hit cap for melee attacks, the spell hit cap has become very important. Recommendation is to gem/enchant to hit the Spell Hit cap, keeping in mind that you can get 3% spell hit from raid buffs (Shadow Priest - Misery), and you can also consume a Hit Rating food buff. Draenei of course have another 1% hit that they do not need to gear for due to their aura.

Spells have a miss rate of 17% (16% for Draenei) against level 83 (Boss) targets, but this is lowered to 14% (13%) after raid buffs. Spell hit correspond to hit ratings as follows::
17% - 446
16% - 420
14% - 367
13% - 341

A common misconception is that you "have to hit before you can crit." This is a fallacy and illustrates a misunderstanding of the attack table. (Note that this is in reference to white damage which uses a single roll system.)

A second misconception is that a miss is a "missed opportunity for a WF proc" and that more Hit Rating will generate more WF procs. This misconception is generated from the flawed assumption that all swings are possible WF procs. However only swings that are outside of the WF cooldown are eligible to proc WF. A good portion of your autoattack hits will never be capable of producing WF procs. A 5 minute fight with no flurry would see 115 white swings with a 2.6 speed weapon. A Shaman might look at that and think that 0.36 * 115 = 41 possible WF procs, but that is incorrect since each successful proc locks out 1-2 hits that follow, shrinking the pool of actual eligible hits. It is actually quite difficult to calculate the number of attacks that you *should* have producing WF in a given amount of time, and that is why we rely on simulators to generate the EP value of Hit Rating.

Another good source is on BIGHITBOX form Stoneybaby with his
Enhancement Shaman Hit Rating FAQ

All your Enhancement Shaman hit cap, hit rating, hit percentage questions answered. What does it mean to be Hit Capped as an Enhance Shaman? Being hit capped means that you cannot miss your target with your spell or strike. For an Enhancement Shaman, we only go for the Spell Hit Cap which means that we have a 100% chance to hit our targets with spells.

Why should I get hit capped?
Theorycrafting from across the WoW community has shown that getting spell hit capped has the single greatest contribution to DPS for the Enhancement Shaman.

Why shouldn’t I go for the melee hit cap?
To be Melee Hit Capped as a dual wielding player would require such a significant investment in Hit Rating that all other stats would suffer. I’ve seen in my personal experience that getting Spell Hit Capped results in about a 10% miss on melee strikes, which is more than acceptable. Just to give you an idea, your melee hit cap as a dual-wielding Enhancement Shaman on a raid boss is 656 Hit Rating for alliance and 689 for Horde. So don’t bother. Hit, Hit Rating, Hit %, how do I know what to look for? With each of the caps below I’m just using Hit Rating, which for practical purposes is the easiest way to optimize your gear. At level 80, 26.232 hit rating is equivalent to 1% spell hit. (Courtesy of Wowwiki)

What is my raiding hit cap?
Alliance: 341 Hit Rating
Horde: 367 Hit Rating
This is to achieve zero missed spells at level 80 on raid bosses (level 83) with a Shadow Priest’s Misery or Balance Druid’s Improved Faerie Fire. Woah. Wait. My hit cap depends on other players? What if they’re not in the raid? Yes it does depend on other players. With Misery and/or Imp Faerie Fire up the hit cap is significantly reduced on bosses. If you don’t have a Shadow Priest or a Balance Druid then your hit caps are:
Alliance: 420
Horde: 446

Then how do I gear for raids?
My personal recommendation is to go for the raiding hit caps that assume you have those players in your raid. If you don’t have a Shadow Priest or a Balance Druid then tell your guild leader to go out and recruit them—those debuffs affect the entire raid’s hit caps, not just yours.

What is my dungeon hit cap?
Alliance: 132
Horde: 158
This is to achieve zero missed spells at level 80 on dungeon bosses (level 82) assuming no debuffs. Clearly, if you are only doing dungeons (or if you have gear just for dungeons and another just for raids) then gems, enchants and gear can be optimized for other damage abilities.

What is my soloing hit cap?
Alliance: 79
Horde: 105
This is to achieve zero missed spells at level 80 on level 80 mobs. What is my PvP hit cap? Same as soloing. Why are there different hit caps? To simplify, the mechanic of hitting a mob or player scales according to difference in level. It’s easier to hit something lower level, harder to hit something higher level, and it doesn’t scale linearly. The further apart in level then the more hit required to land a successful spell or attack. Why are Alliance and Horde Hit Caps different? An Alliance Shaman can only be a Draenei who benefit from the racial passive, Heroic Presence, increasing chance to hit with all spells and attacks by 1% And on we go with the elemental treeAnd the only source that I could find with what looks complete about the elemental mecanics was ofcourse the Elitist Jerks forums
Overall Effectiveness: Below cap: Very High Above cap: Worthless

Other Notes:
While this is the most valuable stat to have when not hit capped, it is worthless when over the hit cap. Shaman get 3% hit from talents and can have an additional 1% from the Draenei racial aura. This means that Alliance shaman require an additional 13% hit, while Horde require 14%. This cap can be achieved via gear (gems, gear, enchants) or buffs/debuffs (food, Misery/Imp Faerie Fire). Note that missing a LvB cast will reduce your damage by more than missing a LB cast. Likewise, missing FS will delay the next LvB cast, also causing greater reductions.Intellect
166 Int = 1% crit, 1 Int = 15 Mana, 10 Int = 1 mp5 with Unrelenting Storm, 10% bonus with 5/5 Ancestral Knowledge. Int is the only base stat that will affect DPS, and even then only in a minor way. It's primarily involved with increasing and replenishing available mana.mp5
mp5 is generally worthless to Elemental Shaman, due to the high innate regen (approx 300mp5 from Water Shield, Mana Spring and Unrelenting Storm alone) as well has the mana reductions given via talents (Convection & Shamanistic Focus) and Clearcasting. Gearing for mp5 is almost as worthless as gearing for spirit (ie: don't do it).Spell Power
This is the primary stat for Elemental. Scaling wise, it increases in a linear fashion, but this increases as other stats increase (Crit, Haste, & Hit until capped). One additional point of spellpower will always be worth the same as the previous point.Spirit
Spirit is virtually worthless to Shaman, as there is no equivilent to the talents that allow passive regen to continue while casting. This is also apparent by the way shaman gear is itemised. The downside is that Cloth and Leather gear may not be as valuable if points have been spent on spiritIf you are RESTORATION you do not need one single item with hit rating, hit rating is useless for healers.


You can visit these links if you want to read the complete source of my documantation
EJ-Enhancement
BIGHITBOX FAQ about hit rating for enhancement shaman
EJ-Elemental