Rotation + Mods

Rotation

As a healer, it mostly depends on the situation as to what heals you wanna pull out of your arsenal.  The overall basics are pretty simple and as follows:

> Hit Holy Shock every time its up- build your Holy Power while achieving fast heals 

> Use Judgement when you can- gives back mana, heals you, and keeps your 9% haste buff up

> Be aware of your Daybreak and Infusion proc's- this will keep you mana efficent and produce the best possible healing

> Cooldowns are usually best during high damage phases

> Use Divine Plea as much as you can- it cuts your healing in half, but endurance pays off.  Just be careful when you do hit it, that it does not endanger the tank.

Other than what other cooldowns you have from trinkets or racial abilities, be aware of your mana pool, and be ready to use them at ideal times.

Mods

I recommend mods for the following:

Daybreak

Infusion of Light

Holy Power

Eternal Glory

Judgement

Beacon of Light
Holy Shock

You need to know what your Holy Power is at all times, if your talented correctly into Eternal Glory.  If you get a proc where your Holy Power was not used up, then you will not waste your mana and you will know when you can use it.  I use one mod to keep track of both Holy Power and Eternal Glory.  It is called NugComboBar.  This mod was originally use by rogues and feral druids, but can be used for Holy Power.

Daybreak should never be wasted.  It allows for 2 consecutive Holy Shocks, which happen to be your lowest mana cost spell.  I use the mod TellMeWhen.  This mod allows me to see when Holy Shock is on cooldown, and in doing that, I can tell if Daybreak proc's.  Blizzards built-in power auras also shows your daybreak proc.  So, this mod is more useful in the sense that you know when the cooldown is up.

Infusion is the most overlooked ability of a holy paladin.  Most beginners do not know what this is.  It is in the your talents as Infusion of Light.  Everytime your Holy Shock crits, it reduces the cast time of your next Holy Light or Divine Light by 1.50 seconds.  With Judgement, this is a 1.0 second cast.  Do not find yourself spamming one button and ignoring this proc.  You can use your lower mana cost Holy Light, and if this proc's you can bring a tank up much faster then spamming Divine Light blindly.  I use EventAlert for this.  I turned off all other alerts so that I only see this one.

Your Judgement is now used every available time because of the mana return given by it.  Because of this, having a mod to keep track of it is kinda useless, but if you want to know the timer, or know if it hit or not get a mod for it.  

Beacon of Light has always been good to have a mod for.  If your bol falls off your target it needs to be reapplied ASAP.  I use a mod that covers my judgement timer and my beacon of light timer.  The name of the mod I use is clcbpt.  It is a really wierd name I know.  But it is very basic which I like.  There are alot more beacon of light mods out there.  So, that is something you can play around with until you find the one that fits you best.