Hey there, this is short guide mostly for lower lvls on making money.
Level16 + (Horde or Alliance) Magic Dust:
Magic Dust is a pretty nice way to make money if your a low level. They drop from the dust devils in Westfall and can be sold for a nice sum of money. Twinks are very interested in these and I have found I can sell them for 5g each sometimes. The drop rate is very low but i find i can farm about 6 in one hour. The Dust Devils are spread throughout Westfall in these locations 67,73/ 62,52/ 60,35/ 54,40/ 35,34/ 33,49/ 34,67/ 40,22 / 41,59/ 37, 60. I usually start at one coordinate and make one big circle. Each circle around takes about 7-20 min depending on if you have a mount or not.
Level 1+ (Horde or Alliance) Throat Piercers:
First of all I have to say that if you're on a pvp server and you are alliance it will be much harder to get these. Recently I found out that my server had absolutely no one selling Throat Piercers, and I could sell them for 10-20g to rich twinks who are lazy. Most twinks have absolutely no idea where to get the Throat Piercers, and it's is certaintly one of the best ranged weapons a twink rogue can get. In Tranquillien (Ghostlands, if you don't know where it is look it up) there is a vendor who sells these Throat Piercers for ~9s. Make an alt and get him to tranquillien and give him a decent amount of money so he can buy the Throat Piercers (there is a mailbox at Tranquillien). Now find the vendor man named Eralan (the poison vendor). This guy spawns two random weapons, one at a random time, Throat Piercer's and Sinister Scimitar, but be aware that they despawn too, so check often. Log on as often as possible and check the vendor for the Throat Piercers, eventually you'll get them. I do this all the time and find i can sell them pretty easily.
Level 1+ (Horde or Alliance) Cloth:
Ok this might be common sense, but I know all of you at one point in time have vendored linen cloth, silk cloth, mageweave, etc etc. Well DON'T!:wave: I sell all this stuff for an overpriced amount and usually people trying to level first aid (twinks mostly) will always buy it out. This a simple but effective way in making some easy money.
Level1+ (Horde or Alliance) Buy low Sell high (most common moneymaker):
Always Always Always check AH for twink items that are cheap. I've made tons of money doing this. At one time I bought a Shadowfang for 5g (you might not be that lucky, but there's always that chance) and resold it for 180g. Look for cheap: Shadowfang, Assassin's Blade, Meadow Ring of Eluding, Treebark Jacket, etc. etc. Try typing something in the AH search like Level: 1-19 Rarety: Rare - Armor/Weapons.
Well that's pretty much it it's pretty short but I hope this helps a little bit. I know people are always looking for ways to make money and these are just some ideas.