Healthstones, health pots, use what ya got
The first few items here are universal to all players; anyone can pop a pot or a Healthstone. These are perfect in a fight such as Sindragosa where the entire raid is moving and taking damage at the same time. If you're low, pop a pot or a stone. In my guild healthstones are known as "Stoney crack" because I was in the habit of asking for them so often it was practically after every wipe I'd ask for another. Get to know your friendly neighborhood warlock and enjoy the life-giving boogers they provide.
For Draenei, Gift of the Naaru is a cool little thing, but in an emergency it's not going to save you or anyone else for that matter. I'm not denying it's helpful, it's just not an "OMG I'm at 10% save me now" spell. It's great for heavy raid-damage fights and a nice little HoT to have up when you're dotted up with some environmental effect. In PvP it should be used while you're getting DPS-focused but before your health gets dangerously low.
Pro-tip: keybind a macro for all your stones and pots and abilities. Try this on for size:
/use Fel Healthstone
/use Runic Healing Injector
/use Runic Healing Potion
/cast Gift of the Naaru(Racial)
It's a mashable macro and should be somewhere within quick striking distance in case of an emergency. When a stone or pot is really needed there's simply not time to hunt for it in bags or hunt for a button to click. Hot-keying can make the difference between living and dying.
Now the fun begins: Maelstrom Weapon. (Notations of MW5 refers to the number of procs of this ability, with five being the maximum.) Choosing when to cast a heal with Maelstrom Weapon is purely a judgment call.
Generally with 0-2 stacks, which is 0%-40% cast time reduction, you're better off hitting a few more times to get the stacks higher. Unless it's a dire situation, a healer is going to get that heal off before you can finish your cast. With three stacks a 60% cast time reduction is perfect for getting off a quick Lesser Healing Wave (LHW) in a pinch.
Usually in a high damage fight I'm looking around at about 3 stacks to see how everyone's holding up. Once I hit the 4 & 5 stack territory I know whether the raid, the tank, the melee, or the Stoneybaby needs a heal. If so, inc heal!
We're up to 4 or 5 stacks of MW and we've determined our efforts are best used to throw out a heal. Each of our the three spells has their place in the game. Let's run through them briefly.
Healing Wave (HW) is the big daddy of the group. Long cast, big heal, and huge crits. This is the spell that can make a real difference in a clutch moment. My HW crits fully buffed consistently hit for over 10k. However, because of the 3 second cast time it's not worth a second look without some maelstrom love.
Lesser Healing Wave (LHW) is your sidekick: quick, fast, easy access, but not the star of the show. You'll get some satisfaction from LHW but it's a waste of MW procs over 3. I use LHW when I'm in a tight spot in arenas. This is the exception to the 0-2 MW proc guideline. A LHW with 2 stacks of MW is a 0.9 second cast, not taking haste into account. In other words, it's always inside a global cooldown and with 2 procs will be extremely difficult for an opponent in PvP to interrupt.
Chain Heal (CH) is where we enhancers step in to take care of our melee brothers and sisters -- yes even the rogues. The "smart" feature of CH is that it will find those most in need and hit them. With auto self target enabled we never have to change targets and can mash out a MW5 Chain Heal in some of the nastiest melee conditions. For example, I'll save my MW procs for a Chain Heal on Precious and Stinky's Decimate.
Click to heal
Getting heals on yourself (and on melee with CH) is easy. Auto Self Cast is an option under Interface -> Game tab -> Combat. With that checked all healing spells will automatically target your character, unless of course you're targeting a friendly player then the heal will target them. In other words, you don't have to change targets from your enemy to heal yourself.
As for getting heals on your fellow players, a focus macro or a click-to-cast mod will save the day. For those of you with resto off-specs, first of all my heart goes out to you, but secondly you'll be familiar such mods at Clique and Healbot Continued. Both of these mods enable the player to cast a spell of their choosing by clicking a unit frame. Both of these mods are nearly infinitely customizable with spell and click combinations. For example I use both Shift+Right Click and Middle Click for HW in Clique.
I'll keep an eye on the raid or the party during crucial transitions and pop off a quick Maelstrom Weapon-enhanced HW if someone is on the verge of death. But these click-to-heal mods are purely optional. You can be a great enhancement shaman and never cast a heal on another besides yourself. Personally though I feel an exceptional enhancer is looking out for themselves and their fellow teammates.
The counter argument to my point "a dead DPS does no DPS" is "a healing DPS also does no DPS." Of course the whole logic behind enhancement heals (and thus this post) is to use them only when they are needed in the most dire situations. 99% of the time my MW procs go right into Lightning Bolts or Chain Lightnings. I'm not a healer. (I don't even have a resto spec!) I'm a DPSer. But if 1% of the time I can save the day with a clutch MW5 HW on a key player then I've done my job as an enhance shaman.
My work here is done. Go forth and live to DPS another phase.
May all your hits be crits!
Show your totemic mastery by reading Totem Talk, whether reading Mike Sacco's Elemental edition, Joe Perez's coverage of Restoration or Rich Maloy's Enhancement edition, we have you covered.