How to get money:

[jessic]

List your favourite ways of earning money in WoW
Here's what I did, it worked fairly well.
From level 1-50 I mostly bought things in the auction house and resold for more. On my server this worked well with wool, silk and linen.Every once in a while you might find an epic or rare item which you can buy below it's average prize (check thottbot and allakhazam for those).
From level 50-60 I got most of my money from Large Rope Nets which drop from Devias trappers in Westfall and selling discombobulator-rays(engineering-item). Of course this works best on pvp-servers.
From level 40 on you can farm turtles, with a bit of luck you will find golden pearls which sell for at least 20G a piece. If you can skin those turtles and sell their leather and scales it's even better.

[Mpidis]

Nice first try i guess.+Rep

[kixer]

There are so many...

I've started AH playing when I got my first 100g. I've raised some basic money by means of herbalism and skinning. There are always rich alts that buy everything. Auctioning quest items and rep items is another good way. Never throw away a white item unless you check wowhead or thottbot for it's AH price... Obviously farming makes a lot of money. Be it fish or other materials. I've made a lot of money on the Heavy lockboxes lately. Auctioning limited supply items, especially recipes can make tons of money, if you find where to go to buy them. Market for greens and blues is dead now, only a few twink items can get you rich.

Posting on AH can be tricky. Always find out, what is the best stack size. It's not always 1 or 20. E.g. don't auction Abyss Crystals in 20. Nobody need that much at once.

Outside AH, questing can be very profitable. If you level up your toon, pick any quest you can. If you can't use the quest rewards, always pick the most expensive one and sell it.

I make lots during events. Even the cheapest white item price can skyrocket during events! E.g. Children's week. People buy northern egg, small egg and mageroyal like crazy. Auction them in exact amount needed for achievment, PROFIT. You can make 10 times more money by auctioning 3 mageroyal stacks than 20 mgr stacks... I even bid on no buyout event items in AH during off-season when nobody buys them.

[danbirk]

+rep for a good first try to contribute

[snugglepants]

ive controlled the goldclover market on my realm for so long now, its one of the most expensive herbs on the realm due to the massive influx i put on and the profit ive made is incredible on the 1 herb, i did try to control another market, but buying 200 stacks of 1 item and 200 of another is more risk than i can bother with.

[Swiftle]

Picking herb/mining/skinning is always a good idea. While leveling selling the cloth on the AH is a good source of income especially if it's WOOL. Depending on where you quest items such as the manual pages or STV book pages are a nice source of income. Also make sure every green BoE item you get is either DE'ed or sold on the AH. This is especially true for 40+ items. Here's a quick example I use: weapons between level 41 and 45 give Greater Nether Essence which sells for around 20G or even more. Also what kixer said: if you can't use the rewards always choose the one with the highest price (most of the times it's a weapon). And finally a quick tip on undercutting, it may sound like common sense but anyway: don't always undercut. Here's an example: let say you see 10 times the item X at 20g which is very good price. Ideally you'll want to post your stock @ 19,99,99 or something like this. But then some random guy decides to post his items at 13G. You have 2 options: you either undercut him and sell your items at 12G OR you can still post your items @ 19,99,99. The reasoning behind this is that people will eventually buyout all the low price items and then get to the next lowest price which will be yours. I've been using this for some time and it works particularly well with enchanting maths where prices change very often.