I always decide what i want to pay and stick to that. I always start really low and you always get that look and they say something like "lady please, i pay X ytl for this, i must make a profit."
Stick to your guns and only pay what you think its worth. i usually get bored with haggling so i just say how much i'm willing to pay, if they say no i walk away. if the deal can be done they'll call you back, if not i go elsewhere. I've had a few heartbroken looks after buying something for "cost price" but if they were not going to make a profit then they wouldnt sell.
I have found that a smile and batting of the eye-lashes works a treat too- especially in jewellery shops!..