When you want to make some easy WOW gold to buy your epic mount, this strategy is the best way. Some requirements are needed, and for both frost and fire specs with this strategy and they both seem fine, however the fire spec tends to increase the efficiency.

Requirements: A level 60 Mage with Fire Spec with combustion and blast wave or Frost Spec with Ice Barrier and improved Arcane Explosion.

Firstly, head over to Scarlet Monastery and pop yourself in the graveyard instance. Then kill all the NPCs in the hallway and room as normal apart from the group of 4, if you feel under threat, use mana shield.

Fire Spec: (recommended)
Enable Combustion -> Blast Wave -> Arcane Explosion (repeat until they are all about 15% health) -> Frost Nova (then move back) -> Flamestrike -> Cone of Cold.

Frost Spec:
Ice Barrier -> Arcane Explosion (repeat until they are all about 15% health) -> Frost Nova (then move back) -> Blizzard -> Cone of Cold.

After the room is over, carry on through the next corridor, killing as normal. Stop when you get into the graveyard. This is where your income comes from. Make sure you have full health, mana and plenty of spirits to pull, following the step:

Fire Spec:
Mana Shield -> Combustion
Now run around and pull around 25 spirits. Avoid the elites. Stop pulling if you are down to half heath and then use Mana Potion (if required) -> Blast Wave -> Frost Nova -> Walk away so they can’t hit u before they die.

Frost Spec:
Ice Barrier

Now run around and pull around 25 spirits, avoid the elites. You may need to use Mana shield after barrier drops. Stop pulling if you are down to half health and then use Mana Potion (if required) -> Arcane Explosion (repeat until all are dead, this is usually around 4 explosions)

You have killed lots of spirits, loot them, you will get plenty of World of Warcraft money along with green items, which you can choose to sell at AH or Vendor when you're done. You can carry on into the building at the end and kill the NPC's and boss in there, then come out and reset instance, and go straight back in and do it all again until your bags are full. Good luck with your WOW gold making.