Newbie guide to obtaining wealth
From WoWWiki
interact with vendor 
vendor out of range 
buy/sell after talking
You gain money in World of Warcraft by completing some of the quests (some of them have no monetary reward associated with them), killing mobs and looting their corpses, selling excess inventory items to the vendor NPCs, or learning one or more professions. Don't forget to pick a profession and skill it up as much as you can in the early levels. Trying to max out your profession after you hit a very high level (60+) is a tedious and very undesirable process. As you go up in level, both the quest rewards and the money from mobs increase, as a general rule. Also, humanoid and undead mobs drop loot for more cash per kill than any of the beast type mobs who aren't quest-related. Upon completion of a quest at your maximum level (60 before, 70 after The Burning Crusade, and 80 in Wrath of the Lich King) you receive a monetary reward instead of experience. The same rules apply, you get more money if the quest was more difficult.
interact with trainer 
trainer out of range
As for choosing to learn a profession and selling the product of your labors at the auctioneer, that all depends upon how glutted the market is with that tradeskill and/or those products. If the market is saturated at the moment, if you can afford to occupy the space, hold onto your products and maybe they will be more in demand later. Note that sometimes you can get more money by selling raw materials (skins, ore, gems, and herbs) than by selling finished products (armor, weapons, potions, and other gadgets). This is because most items can be used for various products. However, no player can make all products, and raw materials are of little use to them if they cannot use them for what they need.
In addition, there are always the Trade Channel (only in cities) and the auction house (which appear in all racial capital cities, including Orgrimmar, Thunder Bluff, Silvermoon, and Undercity for Horde and Darnassus, Ironforge, Exodar, and Stormwind for Alliance) where you can hawk your wares. All auction houses associated with a particular faction are linked, and there are also neutral auction houses which are also linked. The neutral auction houses are more expensive to post for sale (on the order of three times), and are not linked to either of the primary factions.
