Shannox, "the dog guy"
The Shannox encounter is a relatively easy fight for a holy paladin to handle. There's not a ton of raid damage outside of the occasional Hurl Spear, and you'll spend most of your time healing the tanks. I like to put my Beacon of Light onto the tank facing Shannox while following the Riplimb tank around. All of my heals get replayed through Beacon due to its 60-yard range, and so I'm able to handle a ton of tank healing without much effort. I also have plenty of time to use Holy Radiance to help heal everyone back up after a Hurl Spear, but you can also use HR or Divine Protection for the Speed of Light sprint bonus. Aura Mastery can help with the AOE fire damage, but I honestly prefer just saving AM for the last phase to ensure that I have it available.
Your biggest challenge when facing Shannox will be avoiding the numerous traps he'll be laying around the room. There are two types of traps, and you don't want to hit any of them. You need to keep your eyes on the space below your character to ensure that there aren't any traps nearby. Mods like Deadly Boss Mods can help alert you when there's a trap thrown at you or someone nearby, but you need to always be watching for traps when moving about the room. The Immolation Traps can kill you if you're not careful, while the Crystal Prison Traps could result in a tank death if you get frozen in one.
The first phase of the fight simply consists of healing the two tanks while avoiding the traps. If your tanks get a large stack of Jagged Tear debuffs on them, you can use your Hand of Sacrifice to help mitigate some of the damage. Hand of Protection won't clear the debuffs, so don't bother using it on a tank.
You'll also want to keep your eyes open for the target of Rageface's Face Rage ability. They'll start taking a lot of damage quickly, although if your DPS is any good, the target will be freed almost immediately. As you kill the dogs, Shannox gains a stack of Frenzy, although his damage still isn't that difficult to heal through.
Phase 2: Bloodlust and Holy Radiance time
Once you've slain both of Shannox's pet dogs, he'll get all upset and start nuking the raid with some AOE damage and slamming your tank. As usual, you'll have someone pop Bloodlust, and the real healing starts. Keep Holy Radiance on cooldown. With Speed of Light, you can use HR every 20 seconds, so don't forget to activate it. You can also use Aura Mastery to mitigate one of the later Magma Ruptures, as its damage done increases with each wave.
Your goal should be to save as much mana as possible for this phase so that you can just abuse Holy Radiance and Divine Light to keep everyone alive. Shannox isn't tauntable, and so if you are faced with the choice of saving a DPS player or the tank, always choose the tank. Otherwise, if you saved the DPS player, now the boss will start killing everyone else, since the second tank isn't anywhere near anyone else's total threat.
Beth'tilac, "the big spider chick"
The Beth'tilac encounter has always reminded me of the Thorim encounter in Ulduar. A small group breaks off from the main raid to go handle the boss, while the rest of the raid stands its ground against an onslaught of adds. Once the tactical squad completes its mission, the boss descends into the arena to face the entire raid's might. It makes sense to me, although I've been known to see similarities in boss fights that nobody else can.
Depending on what your raid leader decides, you'll either be heading up to the top of Beth'tilac's web to heal the tank and DPS up top, or you'll be hanging out on the ground floor, cleaning up adds. If you're staying below, your main healing target will be the tank handling the Cinderweb Drones. Don't bother using Beacon on anyone who heads up onto the web, as LOS will block your heals. You'll also be spot healing anyone targeted by the Cinderweb Spinners, although the damage isn't that dangerous. Your goal is to conserve your mana on the bottom floor and to help coordinate your DPS' efforts while waiting for the top team to get its job done.
The other role on this fight is fighting Beth'tilac on top of her web. To get up top, you can use your Hand of Reckoning to taunt a Cinderweb Spinner. Once it's taunted, it'll fall to the ground, and you can use its web like an elevator to head up. Make sure you let the tank head up a few seconds before you do; otherwise, you'll get aggro. If you're on top of the web and healing the tank and DPS against Beth'tilac, remember that you're probably alone when it comes to healing. Due to LOS blocking heals through the webbing, you're going to need to plan to get every single heal. Keep the DPS players alive with Holy Light, but don't be afraid to drop Divine Light on the tank. Beth'tilac can hit pretty hard, and if you put your Beacon on the tank, Divine Light is actually pretty efficient when factoring in Tower of Radiance.
While up top, make sure to avoid the fiery pools where the Meteor Burn will land. It will pop a hole in the web, so you want to get out of the way before the meteor lands. If you're careful with your positioning, you can get into melee range of the boss, allowing you to score Seal of Insight procs. After a certain period of time spent attacking Beth'tilac, she'll start channeling a powerful AOE spell. Hop down one of the holes that Meteor Burn made, and then immediately use Divine Plea and stop casting. There's a great window here when you don't really need to cast that much, and so you can regenerate a lot of mana by just sitting patiently until you need to go back to the web.
Phase 2: Bloodlust and Holy Radiance time
After three Smoldering Devastations, Beth'tilac will come downstairs to face the united strength of your raid group. Everyone will stack up on the boss' tail end, and the Holy Radiance spam will begin. She'll be nuking the raid with Ember Flare while stacking up her Frenzy damage buff. Frenzy boosts not only her AOE damage but also her tank damage, so this fight will get harder with every passing second.
Your goal should be to use Holy Radiance to help mitigate Ember Flare while keeping the main tank up as he tries to survive Frenzy. Your tanks will be swapping to get rid of The Widow's Kiss, so be sure to adjust your healing target every time they swap. Cooldowns like Aura Mastery and Hand of Sacrifice become especially valuable as Frenzy stacks up higher and higher. You can use Divine Protection to help mitigate some of the Ember Flare damage. I also find that our Guardian of Ancient Kings can be quite helpful here, as it can assist with both healing the tank and also healing the raid up quickly.
The Light and How to Swing It: Holy helps holy paladins become the powerful healers we're destined to be. Learn the ropes in Cataclysm 101 for holy paladins, study the new balance between intellect and spirit and learn how to level your new Sunwalker. Tanking is a job, DPS is a craft -- but healing is truly an art.