There's plenty of sites focused on earning gold with the least effort, min-maxing the gold game in the way that raiders min-max the gear & stats game. Just My 2 Copper is one such site. Follow those ideas if you want to find the most time efficient ways to earn your gold.
For me, its a middle class approach, I have enough gold for the fun things I want and the raiding stuff I need, but I'm not cornering any markets or becoming so filthy rich that I can collapse the server's economy.
You can look at the gold tracker on the right to see that my techniques result in steady progress. The flat areas are more due to me forgetting to run my tracking program for a few days in a row (still cant get Vista scheduler to work properly over a year later), and the big drop offs are when I buy fun stuff like mini vans or dragons or when my sac became gigantique (the doctor gave me a cream to fix that).
Note - This is how I got to where I am now, not necessarily what I'm doing in prep for a new patch. I really don't do a whole lot, economy-wise, when a patch is looming in the distance, but I'll think that one over and post about it later.
So here's some of my basic moves:
Its no secret...I love 'em. I've got 'em on as many toons as I can. While min-maxing for raids in TBC for a bit I waffled away from mining/herbalism on my main, but even then had Skinning as one prof.
My income is mostly from gathering stuff while I'm out and about doing my thing (daily quest for rep, flying to/from raids & dungeons, flying to sholazar to buy new egg, questing, etc), and then selling on AH.
I like Herbalism & Mining, because I treat them as a passive activity. Fly some place. See herbs. Pick herbs. Sell herbs. Buy Mammoth. I almost never specifically go on "farming" missions, unless there's 15 minutes until raid invites and I've already eaten dinner and the uber gf is nowhere to be found, in which case I'll take a swing around Storm Peaks or Icecrown for some quicky saronite and lichbloom lovin.
Skinning on the other hand is active. Since the mobs are everywhere, you sorta choose when to go skinning or not. So if you like the concept of setting aside 15 or 30 minute killing/skinning sessions, then you might like this one. It is nice because its not dependent upon the random nature of node spawn timers.
If you've not got an AH alt yet, this is a big help. Create a level 1 toon. Run him to the nearest city. Main mails everything to that alt.
There's tons of reasons to do this, however the one for me is psychological. There is a distinct break between when I'm out playing and when I'm doing financial stuff. Having the separate toons helps me mentally separate the activities and I can choose when to engage in either one.
Personally, I like having a guild bank for that mule. It helps me stockpile stuff during times of stupid market conditions. Some coconut destroying the Lichbloom market by listing tons for a few silvers? Just store your incoming herbs in the bank and wait things out. Once the joker is gone, you can trickle your supply back into the market.
Whether or not you want to buy this guy out and hope to deplete his supply at low price and then sell high once he's gone is up to you. I generally avoid the buy low/sell high speculation in WoW because I'm risk averse. If you choose to take the risk, you might be able to profit nicely.
Make a disenchanter
Disenchanting is a big money maker. Your main will bring in lots of disenchantable BoE gear. Some BoE items sell for a pretty penny, but most are worth more as dust.
Yes, you can have a friend DE for you, or if you have no friends you can hire a DE, but the convenience factor of having your own is fantastic.
DE is also for when people try to mess with your gatherables. If you're a miner/herber like me, you deal in raw commodities and you sometimes run into people who try to totally fiddle with the market.
Sometimes its just a kid who doesn't know market values, sometimes its a person trying to play their hand at the economics game, and other times, who the hell knows. Normally just wait a week and they go away. Other times your DE will come in handy for....
In the past, I would have viewed this as an "advanced strategy", but depending upon your server's market, you might need to consider this a basic move if you're to generate suitable profit out of dual gathering.
My old server had a very straight forward Ore market. Gather stuff. Sell it for generally stable price. Ka-ching.
The new server seems to be a much more competitive environment, both in raid progression and in the economy. Seems that there's continuous undercutting, attempts for monopoly on a specific item, barking in trade with a friend to artificially boost the price to make AH listings seem more attractive, and on and on with the schemes.
So I've had to be a little more creative to sell my gatherables.
Somebody messing with Cobalt prices? Craft some entry-level plate armor (either your own BS alt or hired help). Depending on your market, maybe that plate will sell nicely, but more than likely, DE it into dust for max profit.
Somebody messing with Goldclover? Brew up some elixirs. You need to experiment with your own server to see which elixirs will bring the biggest margins, but I've had pretty good success across the board during times when people try a focused financial attack at a specific raw herb.
Eternal Earth is another great example. Well, actually, Crystallized Earth, since that's generally what to sell, since ppl buy it for 10% more than the Eternal equivalent. I've got stacks and stacks of the stuff from mining. But so does everybody, because the demand is pretty low, so the prices are just insane low. So find a JC, craft that ring that only requires 2 Eternal Earths as mats, DE, sell dust, obtain gold.
On a server with competitive business folks or just plain stupid undercutters, you need to search out alternatives since it'll be much harder (or impossible) for a player to dominate all possible outlets for a given material.
Like I said, I used to reserve this as an advance technique, but on my new server, its a way of life, and in fact has replaced nearly all of my raw material sales just to prevent myself from crying over how ludicrous the competition is.
But don't feel bad if you're just selling your ores, you're still going to bring home the bacon, even in a competitive market.
A Penny Saved...
My last note regarding basic middle class economics...
The path to riches is simple....spend less than you make. The bigger the gap, the higher the slope of your own gold tracking chart.
I know, it sounds silly or simplistic, but there you go. Only spend on things you can afford. Do you need to enchant your level 57 alt's gear? Probably not. Do you need to buy that Kirin Tor ring? Its up to you, but personally I've chosen to not go there. Do you need all the JC recipes from Isle of Quel'danas? Not anymore.
Sure, you're fine if you do choose to buy things, useful or frivolous (train smasher, ftw), have fun. But if you're hurting for gold, think twice before spending.
The only place I recommend NOT skimping out is on gear enhancements if you're a raider. When 9 or 24 other people depend upon your performance, a few hundred gold on enchants or gems goes a long way, both in terms of stats, and more importantly, sending the message to your team that you value their time as much as you value your own.