Avoiding the most common ways travelers overpay on currency.
Airport currency exchange counters typically offer the worst rates of any option, so it's worth avoiding them beyond a small amount for immediate needs. ATMs using your home bank's network usually offer better rates than exchange counters, though foreign transaction fees vary by bank.
Notify your bank before you travel so a large ATM withdrawal in another country doesn't trigger a fraud freeze. For a road trip involving tolls or parking, keeping a small amount of local cash on hand is still worth doing even in mostly cashless destinations.