4. Totem Choices
As an enhancement shaman, you're typically either put into one of two groups - the tank group, or a physical DPS group. Your group composition should always be what determines your totem use, not your own preferences - remember that they're supporting four other people other than you!
Assuming you're not needing to use a specialty totem, such as Grounding Totem on the Maiden of Virtue fight or Nature Resistance on Hydross, your standard totems should be as below.
Tank Group:
Stoneskin (Earth)
Grace of Air (Air)
Healing Stream (Water)
Flametongue (Fire) for Warrior/Paladin tank, or Searing for Druid tank
For paladin tanks, Mana Stream is preferred to Healing Stream.
Physical DPS Group:
Strength of Earth (Earth)
Windfury (Air)
Healing Stream (Water)
Searing (Fire)
For physical DPS, WF will sometimes be swapped out for GoA, if you've got more hunters/druids than warriors/rogues, and that case drop Flametongue for the warrior (rogue will usually use poison if WF isn't available). You may occasionally use Mana Spring instead of HS, mostly due to hunters being in the group. The goal is to use your totems to maximize your contribution to the group as a whole.
Remember to tailor your totems to the current encounter you're using - using a mod like Totemus or Sphere can make your totem management much easier.
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5. Profession Choices
Personally, I recommend using two gathering professions while leveling up, and then swapping into two crafting professions at level 70. My recommendation would be Mining + Skinning for leveling, and then swapping into Leatherworking + Engineering, or LW + Blacksmithing.
A quick rundown:
Alchemy: Not really a big benefit. Makes getting consumables easier, but without herbalism it's a poor choice. And imo, herbalism/alch on an enhance shaman is a poor choice

Blacksmithing: Blacksmithing gives access to the Drakefist Hammer/Dragonmaw/Dragonstrike, which is one of the best main-hands available until Tempest Keep and Mount Hyjal, or in 2.4 the Vanir's Right Fist of Brutality (105 Badge of Justice). That's about it, and frankly, it's worth it. Your MH is your key gear piece.
Enchanting: Bleh. Let hardcore raiders stick with enchanting. Without access to rare enchants, there's just no compelling reason to take it.
Engineering: Engineering provides access to the awesome goggles (which many people will never replace), and a variety of handy and occasionally-useful items. Seaforium charges, teleporters, grenades (usable while moving, great for battlegrounds), and the money-making Zapthrottle Mote Extractor.
Herbalism: A good gathering profession for cash, but inferior to mining for your own use.
Jewelcrafting: Don't. Even harder to make money at than Enchanting, and the trinket and epic gems you can get out of it aren't worth it. If you've got money to burn, however, you CAN level jewelcrafting up, make a bunch of epic gems, then dump it for another profession, and keep the gems.
Leatherworking: Leatherworking provides access to the very good Netherscale armor set (chest/belt/bracers), as well as handy items like Drums of Restoration and Drums of Battle.
Mining: Preferred gathering profession, as it helps with engineering and/or blacksmithing.
Skinning: Poorest choice for making money, but a good companion to mining or herbalism for leveling, since it can be used without having to track nodes.
Tailoring: ... no.
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6. Enchant + Gem Choices
First, let's cover the basic enchants, then we'll get to head/shoulders and the fancy stuff. When you don't have access to a preferred enchant for armor, going to a Heavy Knothide Armor Kit is a good stand-in (+10 stam, usable on hands, legs, chest, feet, and shoulders. It's never the -best- option, mind you.
Weapons:
Dual Mongoose is the best choice to start off with, and adding Executioner to your mainhand once you reach Tier5 raiding is a good way to go. If those are too costly, go with Crusader. Yes, Crusader, not Potency. As an enhancement shaman, Crusader outperforms Potency thanks to your high rate of attack, and extra attacks through WF (granting an above-average ProcPerMinute of Crusader). Those are the only three enchants you should consider.
Back:
Enchant Cloak - Agility (+12 Agility) - This is the best option, with no real competitors. Get Major Armor as a stand-in.
Chest:
Enchant Chest - Exceptional Stats (+6 All Stats) - This is by far the best option, providing gains in every aspect. Get Exceptional Health (+150 Health) as a stand-in.
Feet:
Enchant Boots - Cat's Swiftness (Minor Run Speed, +6 Agility) - The best option, but very expensive (8 Primal Air, 8 LPS). Boar's Speed (Minor Run Speed, +6 Stam) is also a good option. For any fight where there's any significant amount of movement, which is nearly all fights, then run speed is the best way to maximize your DPS. With so many raid fights requiring melee to move around a great deal, this helps a lot. Get the low-level Minor Run Speed as a fill-in.
Hands:
Enchant Gloves - Major Strength (+15 Strength). Best option, and it's cheap. No reason to use anything else.
Wrist:
Enchant Bracer - Brawn (+12 Strength). Best option, no reason to use anything else. Note: Never get AP when you can get an equivalent strength enchant (12 str or 24 AP, for example), because Blessing of Kings will increase your Strength by 10%, but not your AP.
Now, that's the basic enchants. You've also got the ability to enchant your head armor, shoulders, and leggings.
Head:
Glyph of Ferocity (+34 AP, +16 Hit Rating) Requires: Revered Cenarion Expedition. Use a HK Armor Kit as a stand-in.
Shoulders:
Scryers: Greater Inscription of the Blade
Aldor: Greater Inscription of Vengeance
Use a HKAK as a stand-in.
Leggings:
Nethercobra Leg Armor (+50AP, +12 Crit Rating)
Cobrahide Leg Armor (+40AP, +10 Crit Rating)
Use a HKAK as a stand-in.
Gems:
There are a variety of gems available from Heroic dungeons, and the usable are listed here:
Auchindoun Crypts (Enscribed Fire Opal; +5 AP, +4 Crit) (Orange) (Yes, Enscribed.)
Steamvault (Shifting Tanzanite; +5 Str, +4 Agi) (Purple)
Blood Furnace (Jagged Chrysoprase; +6 Stam, +5 Crit) (Green)
Shattered Halls (Sovereign Tanzanite; +6 Stam, +5 Str) (Purple)
Botanica (Brutal Tanzanite; +10 AP, +6 Stam) (Purple)
If you're using Rare crafted gems, then use Bold Living Ruby (+8 Str) in every socket, unless there's a socket bonus that's really worthwhile. To fit those, use Inscribed Noble Topaz (+4 Str, +4 Crit) for yellow, and Sovereign Nightseye (+4 Str, +6 Stam) for blue. The green versions are: Bold Blood Garnet, Inscribed Flame Spessarite, and Sovereign Shadow Draenite.
Never gem for +hit, always focus on +crit/AP, you'll get enough +hit through your other gear options, and it's better to have a low +hit than low AP or Crit.
For metagems, by far the best option is the Relentless Earthstorm Diamond (+12 Agi, +3% Critical Damage).
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7. Attack Rotations
This is a critical part of being an effective raider for any class. As a shaman, your global cooldown (1.5 seconds for all but feral druids, who get a 1s GCD) is going to be constantly getting in your way, and you're going to have to learn to work around it to maximize your contribution to the raid. On a pull, your first priority is to get totems down. Simply start your autoattack, and move into attack position while you're dropping totems. If you're in a tanking group, the first thing you want to get down is GoA, then Flametongue (if it's being used), then Stoneskin, then begin your attack routine, dropping Healing Stream and Searing (if no FT) when the GCD allows. If you're in a DPS group, get down WF or GoA, then SoE, then your attack rotation. You want to get your important group-buffs up first, then the weaker support totems down.
Also, because this is a good place to put this - NEVER attack stuff from the front, unless you absolutely have to. Attacking from the front means the enemy can parry you, which speeds up it's next attack. On bosses, this can often kill the tank, so DON'T DO IT.
For an attack sequence, here's the standard attack cycle:
0.0 seconds: Stormstrike (triggering GCD, until 1.5s)
1.5 - Flame Shock (Duration 12s)(CD 6s)(GCD until 3s)
3.0 - (Refresh totem, if needed)
4.5 - (Refresh totem, if needed)
6.0 - (Refresh totem, if needed)
7.5 - Earth Shock (CD 6s)(GCD until 9s)
10.0 - Stormstrike
11.5 - (Refresh totem)
13.5 - Flame Shock
and it continues from there. Essentially, to boil it down: Open with Stormstrike, then use Flame Shock as soon as you can, then use Earth shock. Repeat, weaving in totems and refreshing Water Shield as needed. Flame Shock will do more damage in total than Eearth Shock, but it's ideal to hit an enemy with ES after the first FS, since the DoT from FS will still be ticking. With proper GCD management and no surprises, you'll be using Flame Shock every 12 seconds, just when it expires. This will take some practice, but once you've got the rhythm down, your DPS will definitely increase. Shocks make up a sizable percentage of your damage, so don't neglect them!
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8. Your Role in Karazhan
Gear Requirements:
For Karazhan, you should be in entirely blues, or very close to (trinkets might be green, 1 or 2 other green pieces of gear). I'd really recommend at least 2 pieces of the
Desolation Battlegear, for an easy bump in your +hit. The 4-piece bonus is fantastic as well.
Recommended Unbuffed Minimums:
AP: 1000
Crit %: 20
+Hit: 100
Health: 6000
Now, +100 hit isn't a lot, and some folks recommend much higher values. The problem with +hit is that it's very expensive as far as item budget goes, so try to avoid giving up too much crit/AP to get it. If possible, give up stam and int to get +hit.
Your role:
I'm going to just go through each area and boss, and give a quick rundown of what you'll likely be responsible for. Note that this is just a general guide, and should NOT supersede what your raid leader instructs you to do. Experience is the best teacher, and don't be afraid to try and fail gloriously. Always try to improve yourself, and constantly learn. If you see someone do something you don't understand (and it works!) - ask 'em about it, and see if it'd be advantageous to adapt the strategy yourself.
Attumen Trash: The chargers here fear, so you'll have Tremor Totem down at all times.
Attumen: Smashy.
Moroes Trash: Use magma totem for the large pulls, it'll be a good chunk of DPS, and you're not as squishy as the mages and warlocks

Moroes: You're a good choice to kite the first kill target (usually the shadow priestess, Baroness Millistipe), using Frost Shock and running around the outside of the room in large loops. If you're in the tank group, keep Poison Cleansing totem down to remove the Blind from the off-tank (OT). Interrupt heals with Earth Shock. If healing is tight, and you get Garotted, ask not to be healed, and use Reincarnation after you've died.
Maiden Trash: For the caster pack, use Tremor totem. DPS the dogs summoned by Guardsman, so they don't go after healers.
Maiden of Virtue: Keep Grounding Totem down at ALL TIMES - it'll eat holy fire. Keep as far from other melee as possible, to reduce the chance of her chain lightning zapping you all. Use Healing Stream for sure here, it'll help more than usual.
Opera Trash: Smashy
Opera (Wizard of Oz): Help keep Strawman stunned by using Flame Shock on him. Hit stuff lots.
Opera (BBW): Hit him, don't get eaten.
Opera (R+J): Interrupt Julianne's heal (Eternal Affection, a 2s cast that heals ~50k health) with ES, and purge both their self-buffs (Devotion for J, Daring for R) if there isn't a mage that will be spellstealing them constantly. Remember not to attack Romulo from the back, or you'll get hit with Backwards Lunge. Attack from the side.
Curator: Attack the adds quickly, as melee DPS you'll be heavily relied on to down these fast, before they do too much damage to the group. Use Bloodlust and trinkets a few seconds before he evocates (so that your SS is ready to cast as soon as he does)
Terestian Illhoof: Hit stuff. Attack the Demon Chains as soon as they're up. Help with imps by using magma or Fire Nova totem.
Shade of Aran: You'll be responsible for interrupting one of his schools of magic. Do NOT use a shock unless you know you'll have the cooldown up before he can cast your spell next. Examples of this are when he loads up a special ability (Flame Wreath, Blizzard, Arcane Explosion), or when he just starts to cast Arcane Missiles (use FS, not ES!). You're also an ideal candidate for dealing with one of the elementals that spawn. If your group isn't killing him before he drinks, be ready to use a health potion and/or healthstone after the pyroblast!
Netherspite: You might be asked to tank a green beam. This will suck your mana down to zero eventually. Not a huge deal for you, really. Be careful of void zones, and do NOT attack in the last few seconds when he's switching forms, or you're likely to pull aggro and die on the transition. Help heal during the shadow phase if healers are having a tough time.
Nightbane: Hit stuff. Drop Stoneskin totem for the skeletons, and Fire Resistance totem for NB. Keep Tremor Totem down for NB to help with his fears. Watch for fire patches, and attack from the sides so you don't get tail swiped.
Prince Malchezaar: Don't die to enfeeble/shadow bolts. Listen closely to your abyssal caller, and be ready to move with the group. Again, don't die to enf/sb.
Overall, you're unlikely to top the DPS charts in Karazhan, but you provide a large amount of utility, and great buffs for your groups.
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9. Your Role in Gruul's Lair
For Gruul's Lair, you should be in mostly epic gear, with some blues. Gruul is comparable to the end of Karazhan, so your gear should reflect the fact you've been stomping through there for a while. There should not be any greens left in your gear. Your main-hand
really should be epic, although a blue off-hand is alright at this point, it's not ideal. Gruul is a DPS race, and the raid cannot afford weak DPS.
Gear Recommendations:
AP: 1250
Crit: 23%
+Hit: 100
Health: 6.5k
"But Logros, the +hit didn't change from Kara!" No, no it didn't. If you have more +hit than that, that's not necessarily a bad thing. If you have a LOT more +hit than that, you're either well above minimums (huzzah), or you're sacrificing AP and crit to get there. Don't do that. Get hit as it comes, don't gem for it.
Your role in Gruul's Lair is very simple: Keep totems up, and do lots of DPS fast.
For the High King Maulgar fight, your kill order is:
Blindeye the Seer
Olm the Summoner
High King Maulgar
On Blindeye, INTERRUPT HIS HEALS. If you don't, you are a failure as an enhancement shaman. Use your fire elemental on Blindeye, as he'll die quickly to Maulgar's whirlwind. Use your Bloodlust as directed by the raid leader, or on HKM if the RL doesn't say anything.
On Gruul himself, you have four responsibilities:
1) Never attack from the front. Ever.
2) Don't die to Cave Ins, and don't kill others with Ground Slams
3) Keep totems down for your group
4) Do lots and lots of DPS
That's the order of importance.