Okay, I have been a viewer and reader at MMOwned for some time now, and thought I would share my own unique way of earning gold. It may be more time consuming and less effective than some methods, but can sometimes really cash out big. Overall I have made about 1200 gold (No kidding, eh?) over 2 servers.
My retail account is now expired, so I will share this way with you. It heavily depends on the wow economy on your server.
Okay, first, make a horde or alliance character. Horde, make it a spiffy blood elf. Alliance, a human. These characters look better in the end. Name him/her 'Petstore'.
Then, on your main, purchase or make a full Tuxedo Set. This will help set the mood.
Then, while still on your main, spend about 100g on random small pets IN THE AUCTION HOUSE. Rather than buying one expensive pet for 100g, stay with smaller, cheaper pets but ones that are still unique. For example, the cats for horde or the blood elf dragon pets if your alliance.
If you have enough money to completely buy out the market competition, this helps as well. Send all of these pets, along with some spare change, to your new alt 'Petstore'.
On Petstore, make up a few snazzy macros to sell pets on the trade channel for your corresponding faction. Say you offer "Pickup" or "Mail Order", and surprisingly enough, I always stated I charged 1 gold for Mail Orders, and every single time unless the person was right beside me they accepted the offer. That gives you some extra gold right there.
Make sure to buy some common faction pets as well, though not to many, and sell them as well. The more varietys of pets you have, the better you can sell. (Will Sell any and all small non-combat pets!)
Often, new players / noobs / rich level 70's will purchase pets off of you. The more popular your "store" gets, you can do all sorts of things like grind really rare pets, or even flood auction houses.
Surprisingly enough, as I stated before, this method is long and may not be as effective as some, though if used right along with a bundle of luck can earn you some big cash. Feel free to flame and what not.