Again, I think I feel like jumping into this thread. : )
There are many ways to make money Tahine. You just have to choose which one is the best for you, or do a combination of alot of them.
First: Farming
Most of the time farming of any kind when done exclusively(ex: when NOT leveling) can only net you a certain amount of money/hour, and in my experience, should be looked at in this manner.
If you're farming; whether it is through mining, herb, or killing lowbies for cloth/leathers, you'll probably be able to see within the first half hour how much gold/hour you can rake in. After that, all it takes is finding the best method/place and grinding it out.
Remember: Farming goes MUCH faster after lvl 40 since you can do it at greater speed with your mount.
Second: Playing the stocks
Here you'll need a little bit of starting cash. It's basically a buy low/sell high game. Instead of money per hour here, you have to look at this rather as a percentage return on your investment.
I personally did mine with ores/bars. I started with copper, and would buyout anyone who would go lower than 1G. I'd hold onto those until the prices went back up to at least 1.75G and just resell them. After that, I did the same with tin, bronze, silver, iron, gold, mithril, and truesilver(in that order). These bars all get progressively more expensive, so you never really make a bigger percentage, you just invest more and therefore get greater returns(example, buying gold at 10G and reselling for 17.5G. No better ratio than copper, just more invested and more returned).
The thing to remember in this game is to ALWAYS have some gold on you to invest on those really low prices. Some new miners will sell for low, as will those who want the cash right aways shouting in the trade channel. It's always a good idea to have some kind of money to buy out these low prices.
Lastly, it's always great to disersify and broaden your "portfolio"(items which you check whenever at the AH) as you make more money. Start small, and work your way bigger. Spider's silk, blue items, and enchanting supplies can all be used to make money too(along with many, many others that you might not find so much competition in. I had a friend control the hide market and did very well for himself in a week or two). Enchanting supplies also don't cost any money to list in the AH, which brings me to my next point....
Third: Disenchanting
This one should be examined at a risky business. Sometimes you make money off of what you disenchant, and sometimes you can lose some.
Easy way of doing it. Start with buying lower level green items that are low in price at the AH. How low of price? You can either get the add-ons auctioneer and enchantrix to do it for you(using methods already specified in this forum), or do it yourself.
For example, I've found that buying lvl 15 items for less than 15S usually nets me some profit. lvl 25 or less, I buy at 25S or less, and lvl 35 or less, I buy at 35S, but my profits aren't superb and I really gotta select my times to sell my enchanting items, so there are obviously much better ways. I haven't gotten to the higher levels of disenchanting yet either, but at my current position, I started with 30G overhead and had over 100G worth of supplies selling(although I did some buy low/sell high at the same time to increase profits).
This is just what I've found though, and you'll have to do your own research if you don't use the add-ons. You can make quite a bit of profit from this, you just need overhead like the buy/sell game.
Now, onto my most unpreferrable and slowest method to make money...
Fourth: Crafting
Although this can possibly cost you the most overhead since you need to skill it up, it can also be a reliable way of making income. In terms of crafting, you should always try to calculate how much money to make per item you craft. Ex: Calculated mats = 50S, Item price = 75S, profit = 25S per.
I don't think I really need to go into detail into the methods of doing this, but I think I can offer some advice. First of all, don't take the lack of your item on the AH as a bad thing all the time; sometimes it can be very good. Also, think of any advantages the items you make might have over others in the AH.
Just be smart about it and remember advertisement goes a LONG way. Just a little example, I used to make alot of throwing axes and darts to make money before. Most people wouldn't even think of looking these up in the auctions, and would think even less of buying them.
When I looked at the items though, I saw dollar signs. I put them up in the auction at ridiculous prices(4G for lvl 35 throwing axes, for example) and started shouting out in the trade channel that they were for sale. In my the trade channel, I'd mention that they were for sale and that they were great for warriors since they grant extra stats in the ranged slot. It didn't take long before the first sales rolled in, and many more afterwards.
Again, this is my own personal example and it might not work in your server/economy. It's just used to show one method of many to the madness of making money.
Hope that helps! I might put together a full guide some day, but I'll offer this in the meanwhile. Hope all those who can't make cash get some ideas!
(To those who already do any of these for cash: please don't kill me ^^)