The first thing you should do is go read what our resident shaman expert, Matt Rossi, says about the overall changes to our class in Echoes of Doom, just to make sure you still want to stay Elemental (Part 1 and Part 2). For my part, I leveled to 70 as Elemental and saw no reason to switch as I worked my way up the new Wrath talent tree. Since we've already been over the new spells, the point of this post is to simply recommend a build for you. So let's get a-buildin'!
Both the PvE and the PvP specs start the same way. Take all 10 talents on the first row of the Elemental tree (Convection and Concussion) and put 5 points in Improved Healing Wave on the Resto tree. This is probably no different than your spec before Echoes of Doom.
PvE and PvP are the same here too. Max out both Call of Flame and Elemental Warding, which will improve both your DPS and your ability to survive. (That's right, elemental shamans are all about FIRE now.) Raiding shamans, on this tier you should also put 3 points into Ancestral Healing so that when you off-heal, your targets can reap this potential armor-increasing benefit.
On the third level, both PvE and PvP should take Elemental Focus and all 5 points in Elemental Fury, which are both talents you probably had before the patch. PvE can take all 5 points in Reverberation, but PvP should save 3 of these points for later.
Both play styles should max out the points in this tier for Eye of the Storm (familiar talent) and the new Improved Fire Nova Totem. Now some of you will say that PvE shouldn't be using Fire Nova totem and I'll partially agree with you. No, you shouldn't be using it in raids or instances. However, you can use it carefully in PvE and questing (which I've done) and it can be extremely useful because of its slowing effect if you get mobbed.
All play styles should max out Unrelenting Storm and take Call of Thunder, which is now a prerequisite to Elemental Mastery. PvP styles should take both points in Storm Reach because it will help your Thunderstorm spell later.
On this tier is everyone's favorite, the delicious Lightning Mastery, which all elemental shammies will want to take. Although I've included Elemental Precision in both builds for its improved chance to hit, you could argue that since this talent also about threat reduction PvP play styles could substitute Ancestral Healing for it (see Tier 2), or whatever else floats your boat.
Elemental Mastery, need I say more? And go ahead and max out Elemental Shields while you're at it.
Here is where PvE and PvP styles start to branch away from each other on the talent tree. Although both play styles will want 5 points of Lightning Overload (even though it seemed to proc less often for me on beta than it used to on live realms before Echoes of Doom), only PvE raiders will really want to max out the new Elemental Oath, which buffs the entire raid or party for spell crit when it procs.
This is a very interesting tier for each play style. PvP players can skip Totem of Wrath, but for PvE players it's a must-have raid buff. All play styles will benefit from Lava Flows which helps Flame Shock now and will help the Wrath spell Lava Burst later. Astral Shift is obviously a PvP-oriented talent and should be maxed out for that play style, but I put 2 points into it for PvE anyway because shamans can be so devastated by fear, stun, and silence effects in any situation.
Tiers 10 & 11
For PvP, you should max out both of these tiers to grab both Thunderstorm -- a nifty new pushback spell for us -- and Storm, Earth and Fire. For PvE, both of these talents might be considered a waste of points. For the purposes of this post, I didn't include them in the PvE talent build. However, in practice, as a PvE shaman who breaks all the rules, I have used Thunderstorm for questing (carefully, as I described with Improved Fire Nova Totem) and found it a lot of fun. Still, on balance, people will probably flame me for putting it into a PvE build so I left it out, preferring to sprinkle these points elsewhere and take Ancestral Healing too.
Here are the links to the two builds I used above: