I was in a raid a few nights ago with a newer holy paladin healing alongside me. We were fighting Blood Queen Lana'thel, and a friendly shadow priest blessed me with a Fear Ward. As soon as the AoE fear phase came, I was immediately pressing my Cleanse macro to save the healers. I managed to dispel 3 of the fears in 4 seconds, including the other paladin. After the fight, he asked me how I was able to click on his unit frame and click Cleanse before the fear was over. He had no idea that you could cast a spell on someone without them targeted.
I've talked about holy paladin addons before, and touched on the importance of using mouseovers to minimize your reaction times. It's true that addons can improve your performance and that they're important in squeezing every last drop of healing out of your paladin. However, there's something even more basic that needs to be in place first-- keybindings. No matter how fast a player is at clicking, it's simply impossible have the same reaction times as a player who is using their keyboard to activate their abilities. In addition, having your spells bound to the keyboard will make your addons and macros even more potent, as you'll be able to combine the two for the optimum healing setup.
Find a replacement action bar
The default Blizzard action bar sucks. That's really all there is to it. It doesn't support even the most basic features, and is so inflexible that it will undoubtedly hold you back. There's a ton of action bar mods out there, and most of them are robust enough to perform the tasks we're going to ask of them. I personally like Dominos, but I have several friends who prefer Bartender. Regardless of what addon you choose, it's important that you familiarize yourself with it and customize it as you see fit. It's important to play with a UI that works the way you do, so don't feel constrained to copy someone else.
The key to binding your keys properly is to sort your spells into different categories, and then making bars for each category of spell. The categories I like to use are: core spells, secondary abilities, lower priority spells, clutch / time-sensitive moves, and cooldowns. We also need to differentiate between keys on the keyboard, since every key is not created equal. Assuming you use W-A-S-D to move, the best keys are immediately next to those, the second best keys are two keys away, and the lesser keys are further away. We want to put our best spells on the best keys, and our worst spells on the worst keys.
The first bar
I like to have my core spells on a single bar, and I center this along the bottom of my screen to provide a foundation that I'll build upon later. You want to keep your bread and butter spells grouped together for easy access. I keep these abilities on my first bar, in this order:
This action bar is going to be your go-to bar, and you need to know which ability is bound to which button without guessing. I like to test this out in random heroics via the dungeon finder. I'll hide my main action bar, and try to heal my way through on memory alone. It will sear the actions into your brain, and you'll be able to heal in a high pressure raid without having to look down and see which button Sacred Shield is on.
The second bar
Next, I like to build a second bar full of buttons, and these are the moves that I need access to on a regular basis, but they're not the highest priority and I usually know I'm going to use them ahead of time. I place things like Aura Mastery, Divine Plea, Hand of Sacrifice, and Hand of Salvation on this bar. I use the Shift key to access these spells, since I'm typically waiting to cast them at the right time, and I'll have plenty of time to press Shift and the proper key. You don't necessarily need to memorize the keybind for every one of these spells, but you should at least be able to quickly look and then press the right key combo to activate the spell.
The third bar
I throw all of the junk that doesn't really need to be bound on a large third bar, and these are spells that you don't use on a regular basis or that you would only use out of combat. This is where I put things like individual Blessings, Righteous Fury, Holy Wrath, Resurrection, Consecration, and Divine Intervention. It's important that you have these abilities on your bar somewhere, but they're so low-priority that you don't need to waste keyboard real estate by binding them. The key is knowing which spells can go on this bar, and which you should bind instead. I like to say that if I use a spell every time I'm in a raid, it deserves to be bound. If I only use it every few raids or in a very particular situation, I'm probably fine just clicking it when the time comes. I mean, will a shortly delayed Exorcism really cost me that much?
At first I tried to intersperse clutch spells throughout my other bars, but we just keep accumulating them and so I finally made a separate bar just for these. Most of them are bound to the high value keys, like Q, E, R, and F. These keys are the easiest to push, so you should put anything time-sensitive on one of these keys. I use the F and Shift F binds to handle both of my primary Hand spells, Freedom and Protection. Again, both of these are mouseover macros, since if I'm using Hand of Protection on someone, it usually needs to be quick.
I also bind E and Shift E to my Hammer of Justice and Arcane Torrent abilities, which puts both of my PvE interrupts close to each other. Hammer of Justice is a very underutilized ability, especially by holy paladins, even though it can be incredibly potent. Try using it on a casting mob while clearing trash to help your tanks out, and it can save your life if Righteous Fury causes you to draw aggro on one of Lady Deathwhisper's adds.
Both of my lifesaver moves, Divine Shield and Divine Protection, are found on my Q key; I know to go there quickly any time I'm at risk of dying. I actually use a cast sequence macro with Divine Shield, so if I push it a second time it activates Divine Sacrifice. This lets me keep DiSac close without costing me an additional binding to remember. My R key is home to my mana regeneration buttons, namely a Runic Mana Potion and my Meteorite Crystal. As you can tell, I like to put common buttons together, as this is really the only way I can remember where everything is at without losing my mind.
The bottom row
It took me a really, really long time to bind anything to the Z key. I loved the ability to unsheathe my weapon on demand, which was great for both screenshots and showing off. However, thanks to the Valithria encounter, I finally found a button combo that made it worth giving that ability up. I now have a cast sequence macro that ties together Avenging Wrath (usually on my second bar), Divine Illumination (also a second bar move), and activates my Talisman of Resurgence. I push Z-Z-Z and I go from a meek holy paladin to a glowing beacon capable of healing massive dragons with a single cast.
My X and C keys are usually reserved for custom fight macros, such as one that switches my aura to Frost Resistance once Lady Deathwhisper transitions into phase2, or another that puts a Hand of Protection on Deathbringer Saurfang's target in case a Taunt misses. It's important to have a few free keys to use for things like this, so that you're not offsetting your normal abilities when you have to add another button to your repertoire. It's the little things like this that will improve your play by miles, and often in very noticeable ways. Just having your buttons in order can cause you to literally save a life.
I use V as my go-to key for spamming, specifically Cleanse. I'm able to move my thumb up from my spacebar to use V, and so I can actually run and Cleanse without any issues. This makes doing things like dispelling Necrotic Plague on the Lich King encounter pretty trivial, and also allows me to dispel the raid in record time. Another fight that requires quick dispelling is Rotface on heroic mode, as the diseased player will die pretty quickly without a dispel since they take greatly reduced healing. Make sure you put Cleanse somewhere comfortable for your hand, and make sure you're quick on the draw to use it. The mark of a great healer is a quick dispeller.
While I can share with you how I have my key binds set up, these buttons only work for me because I'm used to them. Feel free to experiment and make up your own combinations, as long as you're working towards the goal of binding as many keys as possible. It may feel weird at first, but over time, it will make you a much better player. The longer you play with your keybinds, the more natural the feel to your hands. I am pretty sure I could play at about 95% performance with all of my bars turned off, and I frequently test myself in heroics by disabling them. It's one way to make an otherwise boring run through Azjol-Nerub interesting again.
The Light and How to Swing It (Holy Edition) is dedicated to helping holy paladins become the powerful healers that we're destined to be. If you're new to the paladin's healing ways, you can learn the ropes with our Holy 101 article. We also have information on how to keep a tank alive, how to heal a raid when necessary and how to beat the GCD. Tanking is a job, DPS is a craft -- but healing is truly an art.