How do i Heal in 5 Man outland instances?

I know it sounds a stupid question but im very inexperienced at healing, always been shaodow and not realy had to heal before exept in an emergency. The problem is im now 31 points in holy and the rest in disc so ive been doing alot of 5 manners as main healer but i got so many different heals, i get confussed and either run out of mana or just plain mess up. Do i spam greater heals? or renew and flash heals? if anybody could give me a good technique for 5 man instances that would be realy real helpful.

PS thanks a bunch folks.