Not sure if this is a repost but anyways...
so what u need is to find an item thats a reasonable price , say like the butcher for 50g( don't necessarily have to buy an item if you already have it ) , buy it and put it up for say 100g, log onto a different character and spam trade chat "WTB butcher paying 150g" or some random number, people check the AH and buy it and will try and resell it to you, tell them sure and set a meeting place to make sure they buy it, and watch the AH until its gone... if its still there when ur about to trade i just ninja log.
has worked countless times for me and have made alot of money with this
- hope it helps