Depends on your talents really.

For shaman (with CL talent): LB, CL, LB - rinse repeat

For druids on bosses (on trash just go wrath, starfire rinse repeat): starfire, insect swarm, moonfire, starfire, wrath, starfire, wrath

You may want to check: WotLK castsequences for shaman/druid (theorycrafting/long)