This post is written for the Blogging Carnival over at JustMyTwoCopper.org
These are three of the simplest tips I can give for someone with limited time.
Simply set Hearthstone to your preferred banking location. Then take a portal to your desired zone of transmutation for living elements.
Hyjal - Fire
Deepholm - Earth
Vash'ir - Water
Uldum - Air
Make your transmute, come back, post on AH and profit.
Check prices of pyrite ore and pyrium bars. 2 ore = 1 bar. If ore is selling @ 10g per ore (typical on my server) and bars are selling for 30g per (again typical on my server) simply buy out all the ore and smelt. Take Cold's advice and smelt and afk log for the night, that way, when you log the following day, you have nice stacks of pyrium bars ready. Post the bars in stacks of 4 and buy up more pyrite ore, repeat process! I made 10k alone on this, in the past 4 days!
Check the prices of Inferno Ink. See if it is remotely close (or higher than) the price of a stack of the following:
Whiptail (your best bet)
Again, I'll use my server's prices as an example. 1 Inferno Ink goes for 150g. Whiptail stacks sell at 180g (roughly). I buy all stacks Whiptail within 50g of my target price for Infernos (150g). Mill all the herbs (takes a minute max with a macro). Convert pigments to Inferno Inks and Blackfallow Inks. You should get at least 1 Inferno Ink per stack of Whiptail and 4-7 Blackfallow Inks. Post all inks on AH, and repeat the process the following day.
There you have it, three simple tips for making a quick buck.
Cheers - Brouck