You'll need money. Lots of it. Here's how to rake in the gold pieces, and afford that epic mount.
Beginner
1) Quest with empty or near-empty bags. Don't just destroy those grey and white drops - they can be sold to a vendor for at least a couple of silver. It all adds up.
2) Your economic potential is directly proportional to your bag space. Take the hit and buy the biggest bags you can afford, and put the ones you're replacing in the bank until you can upgrade your bank slots as well.
3) If you're serious about making money, consider having two gathering skills instead of crafting ones- mining and herbalism are capable of making a silly amount of cash right up to level 70.
4) Don't buy skills, spells or recipes that you will never use - they're a waste of money if they don't help you advance in some way. The money is better spent elsewhere.
5) Don't neglect your fishing, first-aid and cooking skills- level them up when you can. Crafted food and bandages are cheaper than hitting potions or buying snacks from the inn. You can sell your surplus.
Intermediate
1) Install the Auctioneer add-on immediately. It tracks the prices of all items on the auction house, allowing you to spot bargains, and giving you an idea of market prices for your wares.
2) Create a "mule;" an alt stationed in one of the main towns that lives in the bank. Buy him a few bags, and mail him all your loot - leaving your main character to quest. It should save dramatically on downtime and flight fees.
3) Skip on the more expensive enchantments while you are leveling. It makes no sense to spend gold on an item that you are going to replace in a couple of levels' time.
4) Don't be afraid to grind some of the more loot-rich monsters - such as the swamp monster wannabes in Un'Goro Crater, or the Twilight guys in Silithus. People will still want those texts.
5) Use the auction house for selling, not for buying. You may think you need those gloves/boots/hat of rotating fruit, but 99.9% of the time you can get something just as good by questing.
Expert
1) Level as quickly as you can. If you hit 70 there should be a wealth of players eager to buy your unwanted materials and pickups so that they can level their crafting skills.
2) Finish your quests. Those quests that didn't offer any equipment or much experience have been gathering dust in your log, but now offer an easy way of making a quick buck.
3) Solo dungeons ten levels below you. Instances offer better loot than wandering monsters, and you won't get robbed while you're at it. You're not too interested in the bosses here, just the trash mobs and their BOE drops.
4) Don't die. It's a simple one, but copping it while wearing purples makes for an expensive pastime. If it looks like your end is nigh, and if you have time, get naked.
