Or, The “Just Tell Me How To Not Suck” Guide
Disclaimer: I based much of my work upon the EJ thread. It’s an excellent resource, and this is merely my attempt to make it more friendly for those of us who find the math headache inducing. The thread and other sources are linked at the end of my babble.
Part One: Stats
Stamina: A dead healer is useless. Stamina is good! Just take whatever you get on gear, for the most part, though I might keep around a few high-stamina pieces for Really Ouchy Things. Like Maly. Hi, Maly.
Intellect: Know this stat. Love this stat. Int is boosted by Kings! Int gives you mana, crit, and spell power! Int is also your primary regen stat, as it boosts Divine Plea and Replenishment returns.
Spirit: What the fuck, no.
Spell Power: +Heal. Duh. This is obviously a very important stat, but not one I’d worry about terribly because they throw it at you on all of your gear. I believe I entered Naxx 10 with about 1200 in spellpower. SP boosts the effectiveness of your Sacred Shield.
Crit: Crit means bigger heals for less mana. It’s a great stat, especially as you get into more uber gear. Aim for at least 25% for Naxx, and shoot for 30%+ as you gear up in purples, with the exact amount depending on your play style and who you run with. I do love me a good pet crit chicken.
Haste: I consider haste to be a secondary stat. If your gear has some +spell power and int and other tasty stuff on it, as well as haste, well hey! Bonus. I wouldn’t gem or even specifically gear for it, however. If you find yourself in the position of needing to spam Holy Light (HL), then haste is your friend, but save haste for after you have good levels of crit (30%) and mp5. With luck you’d have some haste from Judgements and your local friendly shaman totem, anyhow.
Mp5: Warning: Bubbs in an mp5 rebel.
Crit is greater than mp5 these days, but do not ignore it!
I happily take it if it’s on gear that’s otherwise a massive upgrade and I don’t take much of a crit hit, but I wouldn’t gem for it unless your gear is oddly lacking in this stat. Int and crit are the better stats to gem/enchant for, int especially.
Remember, mp5 is easy to make up without gear-replenishment, totem, wisdom, flasks, etc.
If you come to a raid with crit stacked sky high and only 30 mp5, I’m going to make sad faces at you. Aim for 200 or so before wandering into Naxx. Flash gets a greater benefit from mp5 than crit and yes, you’re still going to use Flash.
Part Two: Abilities
We remain largely two button healers. FoL and HL are still going to be your bosom buddies. You shouldn’t class yourself as a FoL or HL spammer, however. How about spamming whatever is required for the fight? On trash, this is likely to be FoL. On bosses, this can be FoL combined with Sacred Shield (crit boost!) or, yes, Holy Light (o hai, Patchwerk!).
If Blizzard really wanted us to spam HL all the time, why would SS work the way it does? You can compensate for Light’s Grace not being up, honest. If you need a buffer for a ‘slow’ HL to land, toss SS if it isn’t up already, toss a holy shock and an instant FoL if it crits, and then HL. I’ve macro’d an Oh Shit Button just for this (with Divine Favor to guarantee that crit).
I seem to toss more HLs around in 5 mans than I do in raids, but that’s largely because in raids I have other healers to back me up. Of course that was also in Naxx. In Ulduar bosses are mean. 
HL HL HL HL zzzz.
Learn to predict incoming damage. You can’t be perfect all the time of course, but it’s not hard to know that X boss tends to do slow steady damage/spike hard/require you to never take your eyes or heals off the tank ever. Anyway, down to specifics…
Holy Light: Yes, if set up right, we can toss quite a few of these around. If you pile on mana reducing effects then the efficiency of HL and FoL can be rather close. Be wary of overdosing on this spell on longer fights, however, because nothing sucks quite as much as being OOM when you’re needed. Except perhaps being dead.
HL can cause zomg crazy! overhealing but as long as you have the mana keep ticking, it’s not a huge deal.
Flash of Light: It’s smaller than its more lauded cousin, but quick and cheap. Love it and use it, for goodness sakes. It’s great for lulls in action, or for buying time until a bigger heal can be gotten off. It’s also great for spamming (especially with SS) when the incoming damage isn’t enough to warrant a HL.
Holy Shock: Holy shock is a handy oh shit button, or something to toss off while running away from whatever stupid thing Blizzard has us stationary healers fleeing from this time. It’s not terribly mana efficient in comparison with FoL, but damn it’s handy in a pinch. A HS crit means a quicker HL or an instant FoL if you have Infusion of Light. Once you hit 30% or more crit, this becomes more viable for more frequent use as a crit naturally means a cheaper spell cost, but I still wouldn’t use it too much. Don’t use it in place of FoL unless the instant factor is crucial.
Beacon of Light: Because somewhat better than being able to only heal one target at a time is being able to heal two. Beacon is annoying for two reasons: one, it has a short duration. Two, it isn’t cheap. I personally don’t bother with it a lot. Sometimes only the tank is taking damage and it can be such a huge mana sink.
It’s great in situations where there is aoe damage, especially in 5 mans. It’s great to toss on the OT while healing the MT. It’s also great to toss on yourself if you’re bad at watching your own green bar (I am) or when you need to stand still and eat some aoe (#^&^%& mojo puddles! #$%$^% blizzard!) in order to be of any use. There are some simple mods out there to tell you when Beacon falls off and I recommend getting one.
Note: Over healing does not trigger beacon. Neither does trinkets with a healing effect. Pfft.
Sacred Shield: The disc priest in me was excited by this spell, though it works quite differently than any priest bubble. SS lasts for 30 seconds. The SECOND time someone takes damage with SS up, then it creates a buff that absorbs a CERTAIN AMOUNT of the damage based off a percentage of your spell power + 500. The damage absorbing buff lasts no longer than six seconds, and has a six second cool down. Also, while it is up, you have 50% more crit from FoL.
Normally, SS is used on tanks. I have not noticed any rage starvation issues with my pet warrior tank, but don’t cast it pre-pull. It’s damned nice on Patchwerk.
Avenging Wrath: Wings! Admittedly I forget about this spell most of the time and it currently has the annoying side effect of triggering forbearance. It increases healing by 20%. I’m careful using it since it deprives me of my bubble for 2 minutes, but it’s great when combined with Divine Plea to negate DP’s healing reduction.
Divine Plea: DP gives you mana back based on int, though it does reduce your healing output. I counter it with AW as mentioned above, and use it preemptively just like I used to do with mana pots. Its short cooldown means you can use it multiple times in many boss fights. Sadly, Wings has a longer cooldown, but I can still use it more than once, especially when I blow it early on.
Divine Favor: Poof! Your next heal is a crit. It’s useful to follow up with HS for an instant FoL or shortened HL.
Divine Illumination: This is another spell I’m bad about remembering, except on fights that I know are going to be HL intensive. Useful on boss fights to extend your mana pool. If you know you’re not going to need it at a certain point (after an enrage for said HL spamming) then it’s good to use it whenever it’s up.
Lay on Hands: Sure as hell isn’t what it used to be, in a good way. Use it as a last ditch oh shit button on the tank or on you for mana.
Judgements: Regularly judging can be a right pain in the ass. Sometimes you just can’t take your heals off the tank for a moment! For that reason (and healer tunnel vision) I would pick whatever judgment is the least important as far as uptime goes. Use it if you can for the mana/healing, as well as the haste buff for you, but only as often as the haste buff drops off. No need to toss out on every cooldown.
Some say that a ret paladin would be better off judging Light, and a holy paladin better off judging Wisdom, since Light scales better with AP. I’d just go with what I said above and have any meleeing paladin keep up whatever’s the most important for your group/raid.
Hand of Salvation: If you have a moment, glance over at the threat meter, see which DPS is on top, and throw this at them. It’s better to be proactive with this than reactive, since it reduces threat over time rather than immediately.
Hand of Protection: This is your “oh shit the mage already pulled agro” button. It’s also used to force tank transitions. Do not place this spell where you might hit it on accident because HoPing the tank is baaaaaad. Why yes, yes I’ve done this.
Hand of Sacrifice: As a holy paladin I forgot this existed except for Maiden in Kara. I honestly prefer other methods of deflecting damage off the tank that doesn’t put my own health at risk.
Sources: EJ’s Holy Paladin Guide (http://elitistjerks.com/f76/t35975-holy_paladin_guide_wotlk/)
World of Matticus’ Recommended Requirements for Naxx (http://www.worldofmatticus.com/2009/01/05/recommended-requirements-for-naxxramas-normal-and-heroic/)
For gear, I highly recommend Banana Shoulder’s list here. She also has a great list for gems. I seem to use nothing but Brilliant Autumn’s Glow and Smooth Autumn’s Glow, however I also don’t yet have a meta gem to worry about. The Dazzling Forest Emerald was great until my gear shat mp5 at me. If I did have a meta slot, I’d probably lean towards the Insightful Earthseige Diamond. Mm, int. For gear of all classes, this is not a bad resource either.
