I am in no way, shape or form an amazing healer
but I have a disc priest as an alt and I figure I'd post what I use and found helped me alot when I switched over to it.
Mouse over macros with
Grid
#showtooltip Flash Heal
/cast [target=mouseover, exists] Flash Heal; Flash Heal
So what this does is if I have a mouse over (have my cursor over The Tank on grid) it will toss a flash heal, if I dont have a mouse over but I have a target (im running from fire and I need to bubble the tank and he's my target) then it will bubble him.
I have These for my main spells, Flash, Penance, Bubble, Mending and Renew. Another nice thing with these macro's is that it doesn't matter on your current target as long as you have a mouse over target so in raids I would normally keep my main or off tank as my target and if he/she isn't taking damage I can keep an eye on grid and just toss mouse over heals or bubbles to others that need it.