Check your card's foreign transaction fee
It must be disclosed in the card's pricing table and agreement. It can apply to online purchases from merchants based abroad, not just to travel.
Pack a card without one
Cards that don't charge a foreign transaction fee are listed at /us/credit-cards/no-foreign-transaction-fee.
Choose the local currency
If a terminal or ATM offers to charge you in dollars, that is dynamic currency conversion, which Visa says includes an exchange rate and additional fees. Visa says merchants should give you the choice to decline.
Avoid credit card cash withdrawals
Cash advances carry fees and start accruing interest immediately, with no grace period.
Keep receipts and check your statement
Billing error notices must reach your issuer within 60 days after the statement showing the error was sent.