Keep your sense of humor and should a vendor reject your offer just smile and walk away
Determine just how high your willing to go and dont pay more
Always be polite and friendly - they will be more likely to negotiate with you
When purchasing several items ask for a package deal " If I buy all five could you come down on the price?"
Different vendors may have the same item at different prices - ask the vendor about the price explaining you saw if for less
Ask what you best price is for cash ?
All of these tips can work but if the price is unfair be prepared to walk away no matter how much you love the item.