When I still had RAF time on my accounts ( lots of time ago ) the fastest way was to just do the kill quests. Usually it was about 3 or 4 quests to ding.

Killing 10 murlocks/skeletons/pirates takes less than a minute with a lvl 80. When I landed into a new zone it was like 10 minutes per level. Half of the time was consumed by traveling to the mobs place and delivering the quests back.
Also did the instances, but only to complete the instance quests. Never grinded instances one time and another because it was too boring.

For example, the argent dawn quests in WPL are 30% of level each one, and the last quest was almost half level if I don't mistake. Try doing orange and red kill quests for the extra experience.
If you are alliance and run casters, then do the uldaman quests, specially the necklace one because the reward necklace will last you til lvl 63 or something like.