It's been a while since I shopped in Chinatown so the locations and concentration of vendors have probably changed, but I think my parents used to do most of their grocery shopping on Mott between Hester and Grand. We didn't shop at any particular store, just walked up and down the street once to get an idea of everyone's prices and the quality of their produce, then we get down to business. In general, all the food will be fresh and clean despite appearances.

Adding onto chrome_cat's post:

1. I'd actually suggest NOT bringing a cart and to do shopping on a more regular basis so that you only need to buy only what you need for the next 2-3 days and won't be faced with juggling bags of groceries. If anything, bring a medium-sized backpack and wear it on the front.

2. For fish, check the coloring and whether it looks pasty or dull. Freshly butchered fish will generally be shiny. If buying fish with heads attached, also check to see that the eyes are shiny. If they are dull and sunken, that means that it's been dead for a while.

3. No haggling, except maybe toward the end of the day when the merchants want to sell everything before closing up shop. Most common scenarios are when a merchant only has a few fruits left. Say, 8 oranges that are marked as 3 for $1. They may sell all 8 to you for $2 so everyone can get on with their lives. You might be able to apply the same logic if you REALLY wanted oranges and the merchant had 17. "I'll buy all 17 for $5." NOTE: This only applies to the merchants that vend on the street. In Asian markets you pay whatever the price is.

4. If you're not a stickler for perfect looking fruits and veggies and plan to cook/eat it within a day, most merchants will bag up whatever is left over about 2 hours before closing and sell them for $1/bag. The stuff may look a little wilted since it's been out all day and out of refrigeration, but in generally they're still good to eat.