Much maligned historically, the enhancement shaman received a huge boost with the addition of dual wield. Although there are still some unresolved issues, enhancement is a very viable talent tree these days, capable of both solid personal DPS as well as providing some amazing buffs to their party.
I've spent most of my time as Elemental and Restoration, so my knowledge of raiding as Enhancement is more theoretical than experiential. However, the best piece of advice I can give to a new enhancement shaman is to read the Enhance Shaman: Collected Works of Theorycraft thread. There's a ton of important information in there, collected by some of the best theorycrafters playing the game right now. I'll hit some of the highlights, but I'd highly recommend every enhancement shaman read it.
- Thundering Strikes, Flurry, Spirit Weapons, Elemental Weapons, Weapon Mastery, Stormstrike, Dual Wield, Improved Dual Wield and Unleashed Rage - These are the bread and butter of the enhancement shaman.
- Ancestral Knowledge and Shield Specialization - Both of these talents are bad. For a dual-wielding shaman, Ancestral Knowledge is slightly less wasted.
- Improved Ghost Wolf - This is a great talent for the levelling shaman, allowing you to escape a fight that you're not going to win. It's not a great use of points for a raiding shaman, but can still be useful in the PvP side of the game.
- Improved Lightning Shield - LS is one of the most mana-efficient damage spells in the shaman's arsenal. Like Improved Ghost Wolf, it's not that useful for raiding, but it's great for grinding or for PvP.
- Toughness - Shaman make poor tanks. Point for point, you'll get better returns from Anticipation.
- Two-Handed Axes and Maces - For PvE, dual wielding provides a much higher rate of return - better damage and better "up time" for Unleashed Rage. Until Blizzard makes this a learnable talent, it's still useful to have for PvP.
- Enhancing Totems and Improved Weapon Totems - Although not needed for PvP, these are both strong talents for the raiding enhancement shaman (Enhancing Totems much moreso than Imp. Weapon Totems).
- Shamanistic Rage - This is another great talent for a raider and is usually more than sufficient to cover their mana needs. It's less useful in PvP where battles tend to end before the buff does.
- Improved Reincarnation (Resto, Tier 2) - One of the downsides to high DPS that relies so much on spike damage is the tendency to draw aggro (and die). Two points in this talent will allow you to come back mid-fight and still be useful.
- Nature's Guidance (Resto, Tier 3) - The miss rate for dual-wield is 24%, so the more +hit you can get, the better.
An alternative build, primarily focused on PvP, is a hybrid 30/31/0 build, focusing on 2H weapons with enough Elemental talents to still be deadly at range.
Gear

- You want the slowest possible weapon in your off-hand to avoid having it "eat" your Windfury procs (see the thread above for a full discussion). A green 2.6 speed weapon will generally be better than an epic with a speed faster than 2.4!
- Increased run speed is a huge benefit in any fight requiring movement and these are probably the best boot enchants available right now.
- Always choose Strength over Attack Power if given the choice. Avoid Intellect and mana/5: These are "wasted" itemization stats for you - let the hunters have them instead.
- The suggested AP-equivalent (AEP) values for the various stats are (higher is better):
Strength = 2 (2.2 with Kings); Crit rating = 2; Agility = 1.8 (2 with Kings); Haste = 1.5 (as of patch 2.2); Hit rating = 1.4; AP = 1; Armor penetration = 0.25