Ohh, if you want to be a sneaky little bastard and do things the mean way.
Get someone else to do the haggling for you.

Watch over a thread, and get them to get the seller of the item to go down to a price you want, then just swoop in. Send the toricredits, and you've got yourself a no hassle buy (most of the time, depends on the seller).

Firebolty was quite upset with me when I let him haggle a guy down to 18k for 3 or 4, 512 body textures. I swooped in, sent the toricredits and walked away with the deal. Sometimes, raising your competitors bid isn't always the best choice. Sometimes it's fun to let them do all the dirty work for you. I know it's a bit of a dirty way of marketing, but it works most of the time.