I've tried this and had it work for me several times
You will need:
1x Rare-ish Item (Preferably a BoE epic or very good blue)
2x World of Warcraft characters
1x Server filled with idiots
Steps:
1. Take your rare-ish item, for example a Shadowblade (epic dagger) and put it on the AH for a grossly overpriced amount (like 500g or something).
2. Log on an alternate character, preferably one that will get use out of the item.
3. On your other character spam trade with WTB Shadowblade, paying 600g!
4. Pray that someone will see your spam, see it in the AH for 500g and think they can make an easy 100g by selling it to you.
5. Log back on your main to have a nice 500g waiting for you in the mailbox!