I'm a huge fan of assisting the mob for heals.

I have keybinds for dedicated heals to each toon, as mentioned above.
I also have heals, which assist the tank, or assist the tank's target's target looking for a friendly.
I use the assist type heals much more frequently.

Whoever the active toon is targeting gets the heal, if that target is friendly.
Same principle for buffs.

#show Flash of Light
/assist tank
/cast [help] Flash of Light; [target=targettarget, help] Flash of Light; [target=targettargettarget, help] Flash of Light

#show Renew
/cast [target=targettarget, help] Renew; [target=targettargettarget, help] Renew; [target=targettargettargettarget, help] Renew

#show Rejuvenation
/cast [target=focustarget, help] Rejuvenation; [target=focustargettarget, help] Rejuvenation; [target=focustargettargettarget, help] Rejuvenation

Pretty basic, whichever assist method you use. With an FTL, it would be:

#show Spell
/cast [help] Spell; [target=targettarget, help] Spell; [target=targettargettarget, help] Spell