Also, as a last advice (because everyone covered extensively most of it)

Once you're 70, or while you're leveling up to 70. I would recommand you to take a few minutes to actually learn how the two other healers actually heal.
Their strong and weak point.

More importantly take time to understand how AST Earthly Star and Collective Unconscious and recognize the difference between a regular AoE shield (Succor) and a Deployed Adloquium.
Since Healing is Always done by 2 healers, it is important to have a rough understand of your co-heal tool so that you Don't interfer with their Healing.

A simple example would be the AST dropping the Earthly Star before an AoE. This is a visual clue telling you "I'll heal the next AoE" so to put it Simply, Don't start spamming Medica1-2 right after the AoE.

Sometime you'll be teamed with quite competent healers who will use their ogcd very effectively, knowing how these ogcd works will help you adapt and minimise your time spent Healing.


Most people gave advice regarding WHM Healing but I also wanted to point that, beside in dungeons, you'll Always be 2, so keep that in mind.