Hey (: <(Main Disc Priest)
Basically, what everyone else says is correct. I'd like to add that, as a disc healer, expecially low level it is really hard to die. Bubble is very OP, and with the new patch, is even better for low leveled priests.
This was posted awhile ago, so i thought i'd add my rotation in, which helps me a lot, but everyone is different.
Bubble (stop the damage from coming)
Prayer of mending (Prevent that first damage when the bubble stops)
Renew (Even though it sucks, if your fight is a long one, it makes up for 5-10% of the healing)
Repeat (obviously, throw cooldowns in when needed)
I hope this helps, if anyone has any ideas or your own rotations, please help me out also, im always trying to improve.
ps. Can't wait to test out the panda monk class, im guessing it will be alot like priests, but a bit more ritual style, and smoother maybe. (: