Certainly in Asia and Africa this is a must. Everywhere has a local price and a tourist price. Find out what the local price is and start your bidding just below it. Be prepared to accept slightly above it. If the shop keeper won’t go as low as you want, turn round and walk off. Knowing the local language for “too expensive” also helps. If they don’t chase after you with a revised offer, there’s another shop yards away that will. And the guy you’re haggling with knows it.