While there are a lot of guides out there on how to use various healing addons to your maximum advantage, I noticed that among many players who are new or not that dedicated to healing, there still seems to be a lot of prejudice against healing addons in general. People consider them "cheating", think that they are such good players that they don't need them, or might be interested in getting one but find them too confusing to use efficiently.
Is Healbot "cheating"?
I think part of this prejudice goes back to a long time ago, before I was raiding myself. I remember being told about Healbot, Decursive and other addons being so "smart" that you basically only had to push one button and they would always cast the right spell on the right target for you. But Blizzard banned that functionality for a reason, and nowadays Healbot for example certainly doesn't make any decisions for you; it just allows you to get a better overview of what's going on and to react to changes more quickly. Healbot changing the colour of the raid frame of a person that has been hit by a debuff is no different from Deadly Boss Mods telling you about the same thing (and few people would want to forsake DBM or similar addons), and I believe the "click to heal" thing can be achieved with mouseover macros as well, but I suck at macros so installing an addon that does the same thing is simply easier for me.
In other words, I know that different people have different ideas of what's "cheating" and what isn't, regardless of Blizzard's official policy, but unless you're completely against addons altogether, there's no reason to frown upon dedicated healing UIs. They just give you bigger or at least more distinguished icons and health bars and replace the functionality of mouseover macros.
But I'm a good healer anyway, I don't need any addons!
I admit it, I used to think like that. And then I watched a friend of mine play the game one day, using Healbot in a raid, and she obviously saved so much reaction time! I was so amazed by this that I installed the addon myself and guess what, I became an even better healer.
The thing is, WoW's default UI is really not that healer-friendly. It's got a bit better over the years but still... I never had trouble raiding as dps with the default UI, because I could set it to only show my own debuffs on the boss, and if I had to switch targets quickly I just hit tab or used a targetting macro (hello there, Kael'thas in the Eye). As a healer on the other hand, something as simple as Kel'Thuzad's frost blast completely screws you over if you don't have an addon. I mean, you can set the default UI to only show debuffs that you can dispel to reduce clutter, alright, but you can't dispel frost blast so if you use that setting you can't see it. D'oh! Tab through all the people in your raid until you find the right one? You've got to be kidding me. So you frantically look for the right person, finally find them, select them, cast your heal... and they are probably dead, because you only have three seconds to react and cast your heal before the damage kills them.
This isn't even a question of being good or bad at healing, as in knowing which spells to use or how to manage your mana. It's simple reaction time. It's human nature that you can only react to things so fast, and when the game makes healing a matter of seconds, then shaving off even a half-second can make the difference between failure and success. Being able to see the debuffed person highlighted right away and healing them with just a click instead of clicking and then pressing the heal does save time. Even if the addon only enables you to cast your heals a half-second faster, just think of how much difference that's going to make in today's world of non-stop healing in raids! You could be going from casting 120 heals in a four-minute fight to casting 160, increasing your output by a third!
You certainly don't need an addon to heal five-mans, and maybe if you never ever heal anything but the tank in a raid you can get away without one too, but if you are actually raid-healing ten to twenty-five people, constantly having to switch targets, this kind of thing is really a must. I'm pretty sure Blizzard is so used to everyone using these addons that they actually design the fights with these minimised reaction times in mind these days. Who knows, things might change in Cataclysm if healing becomes slower and a bit more relaxed - plus they said that they want to make changes to the UI too, so maybe there'll finally be a built-in "healer mode". Until then, addons it is.
Okay, you've convinced me... but this stuff looks so complicated, it's giving me a headache!
The main big addons that people like to use for healing are Grid, Vuhdo and Healbot. Zelmaru writes a lot of Grid guides and Tam has one for how to set up Vuhdo. From what I hear they are very good addons if you love customisation, but being more of a "give me something simple that works" person, just looking at those guides makes my eyes glaze over (no offense). If you have similar feelings I can heartily recommend Healbot as something that is easy to handle right out of the box. I don't think anyone even needs a guide on how to use it, really. Just install it, go to the "options" panel, under "spells" type out which abilities you want to be bound to which mouse clicks or mouse/keyboard combos, under "cure" set it to show debuffs affected by your class's dispels (so as a priest, you'd select "abolish disease" and "dispel magic") and wham, bam, thank you ma'am, you should be good to go. You can make other adjustments too of course, like changing the size of the displayed health bars, but that's not that key and either way easy to figure out with a bit of trial and error. So no, it being too complicated definitely isn't an excuse either. Come on, give it a try!