As I'm a man from the south with a southern accent, I have to bargain for most things I want to buy. I think it's a kind of game and I need to be part of that and play the game with the sellers to the best of my ability, if I don't want to get ripped off. I usually start at 50% of the quoted price with the florists near my place. The process is actually quite predictable and normally includes funny stories about how high the price was that they had to pay. After a while, they normally agree to sell for around 60% of their original price.
With ceramic sellers, I usually choose some bowls, plates or vases then ask the total bill. I paid 7,000Vnd for a very nice plate compared to my friends who paid 45,000vnd in the shop. They look exactly the same, no mistake. But when you buy ceremic stuff from street vendors, you need to check each item carefully for flaws which they sometimes try to cover with stamps. Don't worry about taking those stamps off before you pay to check that there is no chip or mark. I normally pay about 45% of the first price when dealing with the pottery sellers.
Going to market is even more challenging for me. Most Vietnamese bargain for every single vegetable. I only bargain for veggies if I'm dealing with a vendor for the first time and I generally stand behind another customer to see what the situation is like. After that I will go back to the same vendor as she knows me. I got terribly ripped off by a chicken seller at my local market, paying 50% more than the normal price. I almost went back to shout at her but she's a damn hard woman and I think I better take it as a lesson and never go to her shop again. One thing that I'm always careful about now is watching what the vendor chooses for me...this is really important. Sometimes, after they agree on a cheap price, they pay you back by giving you the bad produce.
It can be a fun way of shopping in Hanoi and Viet Nam. But I think it's important to remember that "you get what you pay for."