I'm not a "healer", per se, but I do have a few heals at my disposal. When I am in a FATE (and not in a party, which is most of the time), what I generally do is target the mobs, then Cure the mob's target (macro: Cure <tt>). My reasoning is, the only person who's in desperate need of a Cure is the person who is currently being beaten up.

Even if that person is running about like a headless chicken, Cure <tt> will hit them. If there are multiple mobs, I cycle through them, checking to see if the <tt> is in need of a Cure.

Is this the "best" way? Maybe, maybe not. But it makes me feel as if I'm helping and I generally get good end-of-FATE awards.

For what it's worth, I also try to Raise the fallen during FATEs. That way, they can get back in the action, which helps all of us. Sadly, on the few occasions when I've been the fallen, I lie there, the FATE ends and everyone disperses, leaving me on the ground.