To be successful in the Wrath of the Lion King then you really need to learn the noble art of gold farming. It takes a while to learn how to farm gold and therefore earn sufficient to make real progress, but here are some real shortcuts that will help you farm masses of gold:
Tip 1: Gold farming needs to have the expanded range that a flying mount gives you. Without it you will be severely limited to regions that can be reached over the ground. Note that in WOTLK you can't use your flying mount until you buy 'Cold Weather Flying' at level 77 at a cost of 1000 gold. So earn a flying mount as quickly as possible.
Tip 2: Make sure that you have maxed all your professions before entering WOTLK. Once you have reached Grand Master status (level 350) then there are lots of gold making opportunities from various professions. Two of the best are gathering and crafting and you will be able to farm gold in Northend and starter areas such as Borean Tundra and Howling Fjord for both Horde and Alliance factions. If you also have cooking and fishing at grand master level then when in Dalaran you can take many cooking quests.
Tip 3: Choose a good gathering profession. Good ones are Mining, Herbalism (sell Fel Lotus, Mana Thistle, Netherbloom) and Skinning. Skinning is particularly profitable and huge prices can be obtained for Cobrascales and Windscales. Don't just sell the Cobrascale for 20g, instead buy some mats and make Nethercobra Leg Armor which can sell for 200g!
Tip 4: Choose a good crafting profession. One excellent one is Jewelcrafting and much can be earned by prospecting and gem cutting.
Tip 5: Round up roaming herds in the starter zones and dispatch them using AOE spells. It obviously helps here if you have skinning profession but WOTLK cooks also demand lots of Northend meats and trades can be particularly valuable.
Tip 6: Search out the best farming spots. The best place to farm eternal fire is at 85,73 in Wintergrasp. This is also good if you want to farm eternal water - try patrolling from 29,46 to 69,52. You can get eternal air by patrolling from 22.63 to 68.73, killing both Whispering Winds and Tempest Revenants.