Know what role you want to be playing.
By 70, you should know what you want to be doing. There's a fair bit of compression in the five man game: often shamans find themselves pressured to be healers, since they cannot tank and there's a lot of DPS out there already. If you want to be a healer, great! I myself play Resto quite often and enjoy spamming Chain Heal... er, I mean, healing with diligence and forethought just like any other healer. (Okay, okay, to get serious for a moment, it's not as simple as spamming CH, but it is a wonderful spell for keeping up with splash damage) But if you want to be a DPS shaman you may have to overcome a lot of resistance and hostility, varying on server and faction. (I find Horde tend to be more familiar with what shamans can do, although Alliance are starting to catch on.) If you absolutely cannot stand healing, don't force yourself to do it. The 10 and 25 man raids are waiting for shamans of all flavors, not just healbots.
In general I find that one of the reasons I prefer raiding to 5 man instancing is that raids allow for more offspec freedom, and nowhere is this more embodied than in the shaman class. The synergy of abilities like Unleashed Rage and Totem of Wrath become far more evident in a 10 man than in a five, when you can afford to stack casters and healers into a single group and melee and tanks into another. (The melee/tanking group is going to love Windfury totem. I know the hunters will be sad.) This makes enhancement and elemental shamans more in demand than they often are in the 5 mans, so hold on and persevere. If you can stand to heal, of course, you can always go as Resto and anger the rogues and hunters by rolling on the DPS leather and mail, or the mages and warlocks and shadow priests by rolling on DPS cloth... and moonkin by rolling on caster leather...hey, at least you won't be rolling on plate, right? If you're going to do this, make it clear up front you're gearing up for an offspec and expect to be allowed to roll. If the group won't agree, don't heal for them, it will just cause hard feelings later.
A lot of this is made easier if you're already guilded or can find a good guild. Raiding guilds will often help gear up a shaman in order to gain access to their various buffs. A guild that helps you get through five man content in order to gain a dedicated enhancement or elemental shaman is investing in the future when such will make their 10 and 25 man raids easier, and I have yet to hear of the raiding guilds that don't like our array of healing options.
Okay, they want chain heal and Earth Shield.
Figuring out what gear to wear.
In the past I've been focusing on mail gear for shamans when listing gear for raid prepping. This is because I'm stubborn and I've been mentally conditioned by tanking on my warriors to wear the highest armor gear possible. Even when I suggest that DPS warriors should wear mail or leather if it has the right stats, I don't really like doing so. So in the past I've focused on mail for shamans.
Ignore this advice.
Some of the best DPS gear for enhancement shamans is leather. There's no way around this. Similarly, if you're an elemental shaman, what gear usually has stats like spell crit and spell damage on it? That's right, cloth. There's a lot of cloth healing gear out there too, although it tends to lack mp5. I took my enhancement shaman into Karazhan wearing the Chestguard of No Remorse, as I liked the raw attack power over the Salvager's Hauberk. As you run Karazhan and heroics and start to accumulate Badges of Justice, you'll start to look over the rewards available and realize that the stats on them often matter a lot more than their being mail or not. One of my elemental shaman guru's purchased the Blessed Elunite Coverings over the Hauberk of the Furious Elements because he liked the flexibility the sockets gave him.
This comes down to taste, of course, but consider the Scarlet Sin'dorei Robes. I've just started toying with an elemental spec, and man, these look solid as heck to me.
Get ready for the unconventional.
Many times as you begin raiding, you will come upon a fight that has a unique element that requires tactics outside of the usual tank and spank to overcome.
This is what shamans are made for. Grounding totems to eat Vashj's stuns and Frost Shock to kite her striders? Shamans have you covered. Heroism to burn through Kael's first shield so that the tank doesn't have to eat a pyroblast? Yay for shamans! Chain heal is always helpful on Gorefiend, and a shaman's ability to self-res can help cope with Shadow of Death. You may be asked to tank a scarecrow with Flame Shock.
The wide variety of shaman special abilities and unique totems makes them the leatherman of raiding. While I encourage you to choose a spec and work to gear and excel at it (and will be writing in the next weeks about how each spec can gear to begin raiding) and I'm not telling you to neglect that role at all (one of the best melee DPSers I know is an enhancement shaman) you do have to be ready and willing to do more, because unlike a lot of more focused classes, you can. Just as a mage has to be willing to use spellsteal in Gruul's Lair, when called upon to use your wide arsenal of abilities to help raid success don't begrudge the loss of focus from your primary role. Yes, it will cost you some on the DPS meters, but what really matters is that the boss dies and your raid doesn't.
Next week, we'll talk about gearing your shaman to step in the door of Karazhan. (We probably won't focus much on badge gear, assuming that as you gear up for Kara you're doing heroics and dailies and not going to have 100 badges to throw at a chestplate. We may or may not dicuss some of the earlier badge gear which is more affordable for the 5 man player.)