I suck at it.
Really, that's all I have to say.
Okay, okay, my total experiences thus far have included one Setthek Halls run and two Utgaurd Keeps. But, really, I'm terrible at keeping everyone up during a boss fight. Usually at least one DPS dies, and I'm unsure of how to improve myself.
My greatest annoyance so far is the fact that I essentially need two different spellbars/UI set ups in order to be an effective healer and still have the same configuration for my usual DPS-mode. I need to be able to see everything that pertains to me in the group as a healer, but I could care less as a DPS. It rather sucks. I also need to find a listing for all those nifty mouse-over macros and start using them - I'm sure that would help as well.
I don't think healing is good for my anger-management issues regarding DPS doing what they should, either. Just the other night, I ran a GDKP ToC25 to satisfy the weekly raid, and one roughly-equally geared hunter out-DPS'd me by a good amount on most fights. Why? Because he wasn't killing the adds. And now that I'm a healer and totally dependent on the DPS to take care of things like that, I can't see this boding well for the growing twitch in my eye.
I'll keep at it though. Maybe it'll grow on me.