How To Win at Kel'Thuzad

Whether you're Enhancement, Elemental or Resto, being able to throw a heal at an ice-blocked target during Kel'Thuzad can mean the difference between a wipe and a successful attempt. Personally I struggled a bit with this, as there's only a FOUR second window in which to 1) identify who's been blocked, 2) find them in your unit frames and 3) cast your fastest heal. More often than not, I failed. :(

Grid to the Rescue
IMO Grid and Clique are the essential tools for successful healing. Even if you're a purely DPS-minded Shaman, having these installed is highly recommended, and your raidmates will love you for it.

1. Open Grid's config window: /grid config
2. Open Status > Auras
3. Type in a new debuff and hit enter: "Frost Blast" (without quotes)
   
4. Find the new debuff in the Auras list, change the color to a blinding bright red
   
5. Also make the priority 99 (meaning topmost priority)
   
6. Open Frame > Border
7. Check your newly-added Frost Blast debuff to enable it
   

The next time someone gets ice-blocked, you'll see their Grid frame highlighted in bright red, so simply click-cast your fastest available heal (Riptide, LHW, NS+HW macro, or maybe Chain Heal if two melee are blocked) then get back to pew pew or whatever you were doing before... playing Bejeweled perhaps?

Don't Stand So Close to Me
Also, if you have Deadly Boss Mods installed (which of course you do!), type /range and you'll see a handy little display of those within 10 yards. Move accordingly.