Use the local currency when traveling

Fordors advises travelers to Deal in local currency: "Before you charge something, ask the merchant whether or not he or she plans to do a dynamic currency conversion (DCC). In such a transaction the credit-card processor (a shop, restaurant, or hotel, for instance) converts the currency and charges you in dollars. In most cases you'll pay the merchant a 3% fee for this service in addition to any credit-card company and issuing-bank foreign-transaction surcharges. DCC is optional—speak up to avoid these hidden charges. American Express card carriers needn't bother; DCC is not offered at all."

Exchange Your Money where feasible for small purchases, local transportation, tips, and the like.