in mexico you have to learn the fine art of bargaining for everything, poon included
i always start out by offering 10% of the price they quote - look 'em straight in the eye and offer 10%, with pride, they will come down slightly, you then offer about 50% of what you are willing to pay. they have done this all their lives so they know by your second offer what your final offer will be. they will come down a little bit more. you then offer 90% of what you are willing to pay. if their next offer isn't about 110% of your target price, then you walk - seriously, walk. they ain't going to come down to your price no matter what. if they do come down to 110% or so then it's an easy matter to split the difference and settle on your target price
it is tempting to complain about how shoddy the merchandise is or something similar in order to get the price down, but don't do this. it isn't 'playing the game' and it shows you to be a fool... why would anybody want to buy flawed merchandise? never insult the seller or their goods
be friendly during the negotiations, and always leave the seller with some pride, even if you break off negotiations
you would be surprised how much stuff you can get for one third the asking price, it happens all the time. that's the way they do it, and it shows respect on your part for their customs, seriously