Instructions
Choose either herbalism and enchanting, or enchanting and mining as your professions. If you wish solely to make money from professions, rather than create gear, then you'll want to pick up two gathering professions. Enchanting is considered a gathering and crafting profession, but the best method to make money with it is by using its gathering method by disenchanting items. You can only choose two main professions, and you can do so by visiting the profession trainers in the five major cities in Azeroth.
Venture out into the highest level zones and click the "Tracking" button on your mini-map. Set it to either mining or herbalism, whichever you chose. Fly above the ground high enough so that you're out of sight of any enemies and pay attention to your mini map. Any mining nodes or plants you can harvest will show up as yellow dots. Navigate to each yellow dot and collect the ore from nodes and herbs from plants.
Click the "Disenchant" button on each green item that you obtain. Green items yield enchanting dust and essences, and both always sell well on the auction house. Do not disenchant blue or purple items, since these items are rare and epic, and thus sell for more on the auction house as they are. You cannot disenchant white or gray items.
Visit one of the major cities in Azeroth, and go to the auction house auctioneer. Enter the item you wish to sell in the "Name" box and click "Search." Look at the average price for the item, and then click the "Auctions" tab. Open your bags and right-click the item you wish to sell. Enter a starting price that's one or two gold below the average price for that item. For example, if you're selling titanium ore, and the average price was 20G per ore, then list yours as 19 G per ore. The lowest price will appear first to buyers.
Go to a mailbox and collect your money. The auction house charges a consignment fee that varies depending on how much your item sold for. You must wait an hour after your auction item is bought before you can collect the money.