Dunno if it has been posted before but here goes.
get a friend, and find some random high lvl who is in Ironforge in the crowded area next to the bank.next, cod him an item (preferably rare) that is not on the AH for a high amount of gold. next, have your friend spam trade saying he wants to buy that item for a very large amount over what you cod'ed it to the guy for. then just have your friend say he found another seller...
all flamers will be executed ^_^