Awareness

Awareness is the first thing a Healer needs to have to be successful. As a healer it is your job to be constantly aware of how the battle is progressing in terms of the incoming damage, how success your heals are at keeping the group up, timing of your spells and being aware of where the individual party members are.

Being aware of the amount damage a party member is taking will allow you as healer to judge which of your spells is most approprate in healing of that target. Say your fighting a boss with alot of AoE or splash type damage. The damage hits your tank for a fair amount of were as all the other party members are damaged somewhere in between moderate damage to small amount. Being aware of this helps a healer decide what spell to use on which party memeber and how well your healing is doing in keeping your party memebers alive and doing what they do best, be it either damage dealing or keeping the mobs focused on them. Also the timing of your spells is crucial because there might be times were you need to heal alot of targets like in the above example really quickly and in the case of a Holy Paladin you are restricted to single target heal spells so being aware of how long a heal will take to cast is vital in keeping all of your party members alive as well. Thankfully Beacon of Light transfers any heals you do to the beaconed party member, which is usually the tank.

Knowing where the party members are helps provent Line of sight issues that can make it so you cant heal party members. This should be job that everyone in the party should be taking care of. But there are times when this does become and issue and the healer will need to adjust there position to get back in line of sight with the party member. Although not at the expense of losing sight with the tank.