Quests

• Daily quests (quests that can be completed once a day) offer a significant earning potential. The average payout for dailies is 13 gold. You can do 25 dailies per day. In addition to doing daily quests, complete unfinished quests. Quest reward gold increases when you hit maximum level. If you skipped any Northrend or Outland quests for the sake of time, go back and complete them. As you complete the quests, focus on your farming professions.
  
  

Professions

• The gathering professions--mining, skinning and herbalism--are the best options for WoW gold farming. Crafting professions have start-up costs and can be expensive to level, whereas gathering professions require nothing but labor. Choose either herbalism and skinning or mining and skinning since you can't track the location of mines and herbs at the same time. Farm every node you see and take your time skinning the beasts you kill as you quest.
  
  

Instances

• At maximum level you can easily solo low-level instances, though not all classes are made alike. The best classes for farming gold through dungeon runs are classes that do a lot of area of effect damage and can tank. Mages and druids are perfect for farming gold, but most other classes can manage with only a few problems. Stratholme, The Dead Mines, Scarlet Monastery and Scholomance are ripe with auctionable items such as cloth and gear. The Dead Mines also has a rare pet drop that sells for up to 10,000 gold on the auction house. Further increase your gold-earning potential by bringing along a few low-level characters and charging 10 to 20 gold for instance runs.
  
  

Auction house

• Play the auction house like it's the stock market. When the in-game economy is good, selling all the materials you have farmed and gathered can help you make lots of gold. Download an auction house add-on, such as Auctioneer, to help track auction house trends. Add-ons can help maximize your profit and prevent wasted time spent farming items that don't sell.
  Another way to make a small amount of gold with the auction house is to keep an eye on the WoW calendar. Periodically there are special events, such as Brewfest and Feast of Winter Veil. Look at the achievements for the next upcoming festival. Several achievements require players to craft or cook something special. Start farming the materials needed for those items as soon as the festival starts and put them on the auction house.