When traveling abroad, get at least a small amount of foreign currency for tips and other unexpected cash expenses before leaving the airport or crossing the border. Although many countries in Europe are now using the Euro, there are still some that are not.
Imagine our panic when we drove across the border from Switzerland — where we had been using Francs — and hit a toll in Italy before we got a chance to find an ATM for Euros. Luckily, there was an option to charge our 1 Euro toll, but other countries may not have that option.
[Ed's note: this is a great way for train conductors on cross-border trains in Africa to earn extra money. The second you cross the border, the currency of the old country is no longer valid, and the trains will only accept currency from the new country. Changing money right at the border offers very poor exchange rates. Therefore, it's wise to try to have currency for the destination country before boarding the train.]