Haggling is the opposite to the just one price policy found at most stores these days. Haggling has largely disappeared in most parts of the western world. However, for expensive goods such as automobiles, haggling can remain commonplace. Also when buying directly from someone (a neighbor or a street vendor rather than a store)
Ideally, you should know the product's worth and maybe the price they charge for it at different places. That, your purse and your eagerness to get the precious object will direct you in offering the dealer a reasonable amount for both of you.
Start with a low amount (not *too* low or you'll hear "Nah, thank you. Have a great day!" Not too high either because, of course, you want to save yourself some cash.
Suppose a car is worth US$ 6000 Start by offering $3500. Dealer will ask for say, $5500 and in that way you may be lucky and strike a bargain.
Hope this helps!