A Karazhan run had too few healers on Friday night, so I volunteered to respec to Restoration for the night. I've been picking up healing gear in Karazhan that nobody wanted, so I felt that my gear would be solid, even if my gear was not totally so.
It didn't go well. My gear was up to the job, but my skills were inadequate. I'm not certain that I was the only source of problems, but I certainly wasn't able to handle the healing problems that came up. We tackled the Maiden of Virtue and Romulo and Julianne, and weren't able to down either one.
In an attempt to get on that horse again, I asked to try to heal a guild run through heroic Mechanar on Sunday. It actually went fairly well.
I learned that it was fairly easy to keep the tank up. Usually just a stack of Lifebloom was adequate, and I could maintain a stack of Lifebloom on a single target without much worry about mana at all. I did still have trouble reacting to many people taking damage--but that was more an issue of reaction than of healing power. (I particularly had trouble noticing when I was the one taking damage. Fortunately we had two priests on the team as well to res me.)
We ended up downing the minibosses, Mechano-Lord Capacitus (though we nearly wiped after killing him, because I didn't notice my polarity had reversed), and Pathaleon the Calculator. We had some wipes and deaths, but I improved dramatically over the course of the run.
The advice I've been getting on healing has been targeted towards a more advanced healer than I am. In particular, I often get advice on the importance of managing mana and avoiding overhealing. I'm sure these are important issues--but before I grapple with those issues, I need to deal with the issues of providing timely healing to everyone who needs it.